Biopolymer Workshop Mauritius 2013 - Proceedings

BIOPOLYMER WORKSHOP MAURITIUS 2013 Proceedings Harnessing the power of biopolymers for improving human wellbeing and enhancing global competitiveness Set ting up of a Bio - based Industr y in Mauritius Mauritius, May 8 -10, 2013

contents

THE PLENARY LECTURERS AT THE BIOPOLYMER WORKSHOP IN MAURITIUS 2013

4

NEW APPROACHES TO ENHANCE “INNOVABILITY” OF INDUSTRY AND ACADEMIA

9

Value-driven Engineering

15

Medical Devices and Biomaterials for Mauritius

18

Potential of Biopolymers

24

A Brief on Research Projects at the ANDI Centre of Excellence for Biomedical and Biomaterials Research

29

CHARACTERIZATION OF COMPLEX MACROMOLECULES

35

AGING CHARACTERIZATION OF POLYMERS

39

Zinc Oxide: The Growth, Characterization and Preparation of Nanocomposites

46

Principal organizers: CE PoliMaT; CBBR, University of Mauritius; COMESA Edited by: Maja Berden Zrimec and Alexis Zrimec Graphic design and layout by: Alenka Paveo, www.paveo.si All rights reserved. No part of this report may be reproduced in any form by any electronic or mechanical means (including photocopying, recording or information storage and retrieval) without permission in writing from the Center of Excellence PoliMaT. Published in 2013 by CE PoliMaT, Tehnološki park 24, SI-1000 Ljubljana, Slovenia ©CE PoliMaT Issued by: CE PoliMaT, Tehnološki park 24, SI-1000 Ljubljana, Slovenia CBBR, University of Mauritius, Réduit, Mauritius VDI/VDE-IT, Steinplatz 1, D-10623 Berlin, Germany PCCL, Roseggerstraße 12, A-8700 Leoben, Austria

The Biopolymer Workshops Approach • Joint initiative of the Global Biopolymer Network • Focus on new generation of young scientists and engineers • Interface of science, industry and policy • Formation of project ideas addressing specific local needs

CIP - Kataložni zapis o publikaciji Narodna in univerzitetna knjižnica, Ljubljana 577.11(082) BIOPOLYMER Workshop (2013 ; Mauritius) Harnessing the power of biopolymers for improving human wellbeing and enhancing global competitiveness : setting up of a bio-based industry in Mauritius : proceedings / Biopolymer Workshop Mauritius 2013, May 8-10, 2013 ; [organizers CE PoliMaT ... [et al.] ; editors Maja Berden Zrimec and Alexis Zrimec]. - Ljubljana : CE PoliMaT, 2013 ISBN 978-961-281-106-8 1. Gl. stv. nasl. 2. Berden Zrimec, Maja 3. CE PoliMaT (Ljubljana) 268238336

• Sharing of state-of-the-art biopolymer knowledge • Formation of multi-disciplinary teams working on concrete topics • Involvement of international and local mentors for student orientation

2

PREFACE

BIOPOLYMER WORKSHOP IN MAURITIUS 2013

SETTING-UP OF A BIO-BASED INDUSTRY IN MAURITIUS

Y

ou hold in your hands the Proceedings of the 2

nd

Biopolymer

action plan for their further development into well defined project proposals. In addition,

Workshop titled “Setting-up of a

dedicated international teams that make up

Bio-based Industry in Mauritius”. The

the core of future partnerships in collaborative

Proceedings cover a selection of

projects are formed.

lectures presented during the Workshop, held on 8–10 May 2013 in Reduit, Mauritius.

The main goal of the 2nd Biopolymer Workshop in Mauritius was to learn, network and

Biopolymer Workshops bring experts from

collaborate in addressing the challenges of

the Global Biopolymer Network to local

setting-up a bio-based industry in Mauritius

environments and integrate them with local

in order to facilitate the use of biopolymers.

R&D and industrial competencies, thus initiating

The material presented here was the basis

collaboration and partnerships. By participating

for the group work resulting in four project

at the Workshops, universities, government

ideas among dedicated teams and creating

officials, industry representatives and the

roadmaps to further activities.

interested public – as the Workshops’ key actors – fuel innovations and establish suitable

The organizing team thanks everybody who

framework conditions for strengthening the

made the second Biopolymer Workshop in

biopolymer innovation system.

Mauritius a success: the participants and numerous stakeholders and their enthusiasm,

Teams of international and local mentors work

the international team of experts and mentors

with Biopolymer Workshop participants to

from CE PoliMaT (Slovenia), CBBR (Mauritius),

identify challenges, value chains, addressable

COMESA, the Harvard University, School of

technological problems and policy issues, and

Engineering and Applied Sciences (SEAS,

create roadmaps to solutions. Through lectures,

USA), VDI/VDE-IT (Germany), the Polymer

case studies, panel discussions and intensive

Competence Center Leoben (PCCL, Austria),

group work, Biopolymer Workshops lead to

the Austen BioInnovation Institute in Akron

outlined collaborative project ideas that

(ABIA, USA), and last but not least, the sponsors.

address specific needs of different industrial, social and consumer segments, and a clear

The Organizing team

3

IntRoDUctIon

THE PLENARY LECTURERS AT THE BIOPOLYMER WORKSHOP IN MAURITIUS 2013 Sujata K. Bhatia Harvard University, school of engineering and Applied sciences, UsA

engineering. Dr. Bhatia has academic experience as a faculty member in biomedical engineering and chemical engineering, teaching and advising biomedical engineering students, developing visionary senior design projects, and authoring biomaterials text books. she has industrial experience in medical device and biotechnology product development, clinical trials management,

Dr. Bhatia serves as an Assistant Director for

intellectual property, leadership of multidisciplinary

Undergraduate studies in Biomedical engineering,

teams, and industry-academic partnerships.

an Assistant Dean at Harvard summer school,

Dr. Bhatia serves on panels and committees

and Associate at Harvard Kennedy school of

for national Academy of engineering, national

Government. she is a physician-scientist with

Academy of sciences, and national science

academic and industrial experience in biomedical

Foundation.

Archana Bhaw-Luximon AnDI centre of excellence for Biomedical and Biomaterials Research, cBBR, Mauritius

novel self-assembled polymers for applications as nanodrug carriers targeting cancer and infectious diseases (tB, malaria, etc); development of hydrogels based on self-assembled peptides and polysaccharides for protein delivery. she is also looking into the use of biopolymers from seaweeds/ algae in (i) medical devices such as biosensors

Dr. Bhaw-Luximon gained her PhD in Polymer chemistry in 2001 from the University of Mauritius. she joined the Dept. of chemistry at the University of Mauritius as Lecturer in 2003 and was appointed Associate Professor in 2012. she forms part of the

4

and (ii) commodity materials. Dr. Bhaw-Luximon was nominated as tWAs Young Affiliate in 2008. she has been involved with a number of activities with the World Academy of Young scientists, organizing workshops and projects for young scientists on the

centre for Biomedical and Biomaterials Research

African continent. Dr. Bhaw-Luximon is currently the

(cBBR) working in the Biomaterials and Drug

President of the chemical society of Mauritius. she

Delivery Unit. Her main areas of research are to: (i)

has been the representative of the University on the

develop tailor-made biodegradable/bioresorbable

national Dangerous chemicals Advisory council

polymers for use as medical devices (ii) elaborate

since its inception.

IntRoDUctIon

Zorica Crnjak Orel ce PoliMat, slovenia

nanocomposites (tio2, ceo2, V-oxide, V/ceo2, ceo2/ sno2, sno2, cuo, cu2o, Zno, cu, Zno/ cuo, Zno/PMMA). she is the author of more than 100 papers, more than 1000 citations, more than 90 papers in conference proceedings, and many invitational lectures at international conferences, universities and institutes all around the world, as well as holding 10 slovenian patents, and a few

Dr. crnjak orel is scientific counselor at the

international patents. she is on steering committees

national Institute of chemistry (nIc), Ljubljana,

for several conferences. she is an evaluation expert

slovenia, as well as vice president of the scientific

for several slovenian and european agencies. she

council and coordinator at the centre of

also serves as a referee for many journals. During

excellence PoliMat, slovenia. she holds a Ph.D.

her work she has won many awards and received

Degree in chemistry (1989). the nIc research group

many grants (British council and Royal society (UK),

works in the field of spectrally functional coatings,

Fulbright grant (UsA), clarkson Potsdam; UsA and

research and development of new materials for

oxford Brookes, oxford, UK University grants). she is

non-conventional energy sources, preparation

an excellent research project leader and has been

and characterization of semiconducting thin films

a successful principal investigator for research

and powders, optical and structural properties

programs, many projects and has maintained

of semi-conductors and composites, optical

excellent collaboration with industrial partners. Dr.

and structural properties of counter electrodes

Zorica crnjak orel has also been conferred with a

and electrochromic materials, preparation

number of innovation awards, such as the B. Kidrič

and characterization of nanoparticles and

award and Krka awards for her M.sc.

Frank Douglas Austen BioInnovation Institute in Akron, ABIA, UsA

than fifteen industry awards, including the Global Pharmaceutical chief scientific officer of the Year Award, the Wolfgang von Goethe Medal of Honor, the Associated Black charities’ Black History Makers Award, the Lifetime Achievement Award from the national organization of Black chemists and chemical engineers, and the Heart of the Year

Dr. Douglas is the president and ceo of Austen

Award from the chicago Heart Association and the

BioInnovation Institute in Akron, ohio, a best-in-

Louis B. Russell Memorial Award from the American

class model for the future of health care delivery

Heart Association, both for his development of high

and innovation. Douglas, a former founder and

blood pressure screening and control programs

executive director of Massachusetts Institute of

for African-American churches in chicago. After

technology’s center of Biomedical Innovation, is an award-winning industry veteran, with more than twenty-four years of experience in health care, pharmaceutical research, and biotechnology.

Douglas joined the Austen BioInnovation Institute

graduating cum laude from Lehigh University, Douglas attended cornell University where he earned his PhD in physical chemistry and his MD. He completed his internship and residency in

in Akron after serving as senior partner, Puretech

internal medicine at the Johns Hopkins Medical

Ventures and, chief scientific advisor, Bayer

Institutions and a fellowship in neuroendocrinology

Healthcare, AG. Douglas has received more

at the national Institutes of Health.

5

IntRoDUctIon

Gerd Meier zu Köcker VDI/VDe Innovation + technik GmbH, Germany

innovation and technology policy, consultation and communication with policy makers and public authorities on regional, national and international level, comprehensive experience in strategy consultation, cluster issues, design and management of national and international projects. In 2007 he was appointed by the Federal

Dr. Meier zu Köcker is the Director General of

Ministry for economy and technology (BMWi)

the Agency competence cluster Germany,

to take over the management of the Agency

Managing Director at the Institute for Innovation

competence networks. In 2001 he was awarded

and technology, iit Berlin, Head of the Department

by the Lithuanian Innovation Agency. since

for International technology transfer within

2009 he is the German representative within the

VDI/VDe-It, and Deputy General Manager at

european cluster Policy Group. Dr. Maier zu Köcker

VDI/VDe-It. He has long-term experience in

is also a member of various Advisory Boards.

Dhanjay Jhurry AnDI centre of excellence for Biomedical and Biomaterials Research, cBBR, Mauritius

employed by the Mauritius Research council. With a group of colleagues, Prof. Jhurry has founded in 2011 the centre for Biomedical and Biomaterials Research (cBBR), a first of its kind in Mauritius. He currently heads cBBR. Prof. Jhurry was awarded the first Best Mauritian scientist Award in 2011 and the first Mauritian Innovator’s Award in 2004. Prof. Jhurry

Prof. Jhurry gained his PhD in Polymer chemistry

founded the chemical society of Mauritius in 2004

in 1992 from Bordeaux-1 University in France. After

and has acted as President for the last 9 years. He

spending three years at Flamel technologies co.

was also chairman of the Mauritius Accreditation

in Lyon from 1992 to 1995, he joined the Dept. of

Advisory council (MAURItAs), from 2006 to 2012. Prof.

chemistry at the University of Mauritius as Lecturer

Jhurry is presently chairman of the R&D committee

and was appointed Professor in 2005. since January

of Mauritius sugar-cane Research Institute (MsIRI)

2012, he has been holding a national Research chair

and was recently appointed Vice-President of the

in Biomaterials and Drug Delivery and is currently

coMesA Innovation council.

Andrej Kržan national Institute of chemistry, slovenia

the use of renewable resources for polymer production. Dr. Kržan is a secretary general & national representative of the european Polymer Federation, and president of the section for Polymers at the slovenian chemical society. He is member of the American chemical society, the central and east european Polymer network, and

6

Dr. Kržan is a senior scientifi c associate at the

the scientifi c council of the national Institute of

national Institute of chemistry, slovenia. His

chemistry, slovenia. For a number of years he has

research interests center on environmental and

served as expert consultant for the Biodegradable

sustainability aspects of polymers and plastics:

Plastics Programme at Ics-UnIDo, Italy. For his high

recycling of waste polymers and plastics,

level of studies at the University of Ljubljana, Dr.

biodegradable polymers and plastics, and

Kržan also received the France Prešeren Award.

IntRoDUctIon

Martin Payer

Majda Žigon

Polymer competence center Leoben, PccL, Austria

ce PoliMat, slovenia

Mr. Payer is ceo of the Polymer competence

Dr. Žigon is President of the scientifi c

center Leoben (PccL), Austria. PccL is the

council of ce PoliMat and a full professor

leading Austrian “center of excellence” for

at the Faculty of chemistry and chemical

cooperative research in the area of polymers

technology at the University of Ljubljana,

and was founded in 2002. since 2003, Martin

slovenia. Her research interests are in synthesis

Payer has contributed to the successful

and characterization of various polymers,

development of the PccL, now comprising an

polymer composites and nanocomposites

annual turnover of € 8 million and employing

with clay and metallic oxides, synthesis of

a staff of 100 researchers. Partnering with

metallic and inorganic oxide nanoparticles,

universities and being fi nanced by industry

functionalization of montmorillonite particles,

as well as by public funds, the PccL acts at

homopolymers and copolymers of amino

the interface between fundamental science

acids and lactide, polymer properties in

and industrially applicable development.

solution and in solid state. she is a member of

Before joining PccL, Martin Payer worked

the editorial boards of journals Acta chimica

as researcher at the sustainable Business

slovenica and the International Journal

Institute at the eURoPeAn BUsIness scHooL

on Polymer Analysis and characterization.

(Germany) and the University of Graz. In

she served as president of the european

addition to his position as ceo of PccL, he

Polymer Federation (ePF) in 2006–2007 and

serves as a member of the supervisory board

a national representative to the ePF for the

of Lenzing AG (www.lenzing.com), a member

period 2002–2008, president of the section of

of the advisory board of the annually

Polymers of the slovenian chemical society

tendered “Dr. Wolfgang Houska-Preis der

in 2002–2008, president of the central and

B&c-Privatstift ung (€ 300,000)” for industrially

east european Polymer network (ceePn) in

relevant research projects (www.houskapreis.

2012, and is an associate member of Polymer

at) and several other boards. Martin Payer

Division of IUPAc (2012–2013) and an IUPAc

holds a Master’s degree in environmental

fellow. Majda Žigon also received the France

system sciences and is currently undertaking

Prešeren Foundation Award as a student at

an executive General MBA at the Universities

the University of Ljubljana, as well as the Boris

of Krems, Hongkong and Washington.

Kidrič Foundation Award.

Gernot Oreski Polymer competence center Leoben, PccL, Austria

Dr. oreski is a senior Researcher and project manager at the Polymer competence center Leoben, Austria. His main fi elds of research are polymer physics and testing, polymers for solar energy applications, weathering, aging behavior and aging characterization of polymers. In addition to his work for the PccL, Dr. oreski serves as lecturer at the Department of Polymer science and engineering of the University of Leoben.

7

chapter I.

THE PLENARY LECTURES AT THE BIOPOLYMER WORKSHOP IN MAURITIUS 2013 Chapter I. POLICY IMPLICATIONS, SCIENCE AND TECHNOLOGY New Approaches to Enhance “Innovability” of Industry and Academia, Gerd Meier zu Köcker

Chapter II. IDENTIFICATION OF NEEDS Value-driven Engineering, Stephen D. Fening and Frank L. Douglas

Chapter III. BIOPOLYMER SCIENCE AND TECHNOLOGY Medical Devices and Biomaterials for Mauritius, Sujata K. Bhatia Potential of Biopolymers, Andrej Kržan A Brief on Research Projects at the ANDI Centre of Excellence for Biomedical and Biomaterials Research, Archana Bhaw-Luximon, Dhanjay Jhurry, Theeshan Bahorun, Vidushi Neergheen-Bhujun, and Sabrina D. Dyall

Characterization of Complex Macromolecules, Majda Žigon and Ema Žagar

Aging Characterization of Polymers, Gernot Oreski, Kenneth Möller, and Gerald Pinter

Zinc Oxide: The Growth, Characterization and Preparation of Nanocomposites, Zorica Crnjak Orel

8

chapter I.

Chapter I. POLICY IMPLICATIONS, SCIENCE AND TECHNOLOGY

NEW APPROACHES TO ENHANCE “INNOVABILITY” OF INDUSTRY AND ACADEMIA Gerd Meier zu Köcker VDI/VDE Innovation + Technik, Germany mzk@vdivde-it.de

INTRODUCTION As a result of accelerated globalization and technology advances, world-wide competition has risen to new heights. Financial markets demand ever-faster growth. And growth – perhaps even survival – depends on innovation. The centrality of the individual opens new possibilities for micro consumers, micro producers and micro innovators and investors. In the globalized and digitalized world, all have the possibility to be connected and act, allowing individuals to participate more actively in society.

Phases of the innovation process

Results

Research

Invention

Development

Prototype

Production

Exploitable product

Commercialisation

Market success

Mass application

Impact on economy

Figure 1: How innovation happened in the past [1]

Looking back in the past, innovation happened different than today. One of the first (conceptual) frameworks developed for understanding the relation of science and technology to the economy has been the linear model of innovation (Figure 1). The model postulated that innovation starts with basic research, is followed by applied research and development, and ends with production and diffusion. The precise source of the model remains nebulous, having never been documented [1]. This model was taken for granted. All research activities were completely disconnected by the market demands. Once a new idea was considered to be promising, additional developing activities were conducted to further develop

9

chapter I.

the idea towards a prototype. In a next step, the

of ideas [2]. The corresponding study also revealed

prototype was further developed into a commercial

that regardless of the type of innovation undertaken,

product. Once the product or technology was

collaboration and partnering is very important to

matured, the inventors started to think how to

innovation.

commercialize the product and technology. It was the time when the term “technology transfer” was created. Many technologies and products have been created by inventors and then had to be put in the markets. The majority of inventions had never been commercialized, since the functional behavior was

As a consequence of the new nature of innovation, many so called emerging industries have been arisen.

Emerging industries can be understood as either new industrial sectors or existing industrial sectors that are evolving or merging into new industries [3]. They are

not according to the market demands or there was

most often driven by key enabling technologies, new

simply no market need.

business models such as innovative service concepts, and by societal challenges such as sustainability demands that industry must address. Many emerging

NEW NATURE OF INNOVATION

industries like creative industries, mobile and

Time has changed. Innovation is no longer mainly

in common that they grow out of already existing

about science and technology. Industry today

industries and hence cut across different traditionally

has to innovate in other ways. Co-creation, user

defined sectors in building new industrial landscapes

involvement, environmental and societal challenges

and value chains that integrate cross-sectoral

increasingly drive innovation today. Key enabling

competences and linkages.

technologies open completely new dimension of functional behaves of products and processes.

Collaborative, global networking and new public private partnerships are becoming crucial elements in companies’ innovation process.

mobility industries or eco-innovative industries have

In the past, industry has started to react accordingly.

Companies have become more and more open and transparent and engaged in a dialogue with their customers; provide them with access to more information and share risks with them; and accomplish

In the emerging new nature of innovation, a multitude

this through co-creation with individual customers

of skills is required for solving complex challenges –

and by involving users in the innovation process.

which is why partnerships and collaborative network

To work with customers and users in entirely new

arise and symbiotic relationships are created between

ways, necessitates changes in business culture and

transnational companies, micro companies and

company skills.

public institutions. As shown in Figure 2, business partners and customers are right near the top of the list for external innovation sources. Internal R&D, on the other hand, lost significant importance and is much further down the list of sources of innovations [2].

It seems obvious that a new nature of innovation inevitably calls for changes in innovation policies and the national framework conditions for innovation [2]. However, it should be stressed that science and technology still remain crucial to innovation. Existing and well-functioning national innovation systems designed to support science- and technology-based innovation has therefore be further developed to meet new challenges from emerging global markets for technology and new forms of global knowledge sharing.

Across all countries, governments are involved in research and education; hence a need for new knowledge and new business skills will also have to

Figure 2: Sources of innovations today [2]

involve governments. Governments are continuously called up to react accordingly to adopt framework

External sources were not only prevalent in the

conditions to innovations according to their new

ranking of most significant sources of ideas; they also

way of origin. New policy tools have been created to

comprised a substantial portion of the overall quantity

better to meet this challenge.

10

cHAPteR I.

CHALLENGES FOR INNOVATION POLICY

In the following chapter, it will be further explained,

Innovation policy gained a new role, although policy

and, thus, high on the agenda of innovation policy

implications of a new nature of innovation remain

makers. As far as europe is concerned, there is almost

sometimes undefi ned and may benefit from policy

no country or region, not having a network support

experiments. the new areas of innovation policy

programme in place [5].

why nowadays regional networks are considered to be a key tool to strengthen innovability of companies

identifi ed a broad spectrum of instruments, including smarter regulations to foster innovation and intelligent

support important role in building the knowledge

REGIONAL NETWORKS AS DRIVER FOR INNOVATIONS

and skills needed to deal with co-creation and user

the regional networking aspect has become more

involvement in innovation. In the recent past, policy

and more prominent in companies’ operations.

public demand to enhance companies’ fi eld of innovation. More and more governments focus to

tools successfully unlocked the transformative power of innovation have been implemented that support industry and academia to increase their innovability. the regional dimension also became more and more important. nowadays, regions have built their innovation strategies on regional strengths rather than to spreads public investments thinly across several frontier technology research fields and, as a consequence, not

to underline the signifi cance of this development, building relations and creating new partnerships between innovation actors, has been included as an explicit dimension in successful enterprises strategies’ [1]. evidence has proven that in the presence of universities, research centers and supporting structures, a geographical concentration of high tech companies has a positive effect on the economic

making much of an impact in any on.

performance of those companies [5]. As a result,

Innovation policy has also to acknowledge that

clusters) play a key role in driving innovation, regional

traditional boundaries between manufacturing

development and competitiveness.

knowledge-intensive regional networks (also called

and services are increasingly being blurred [4]. the success of manufacturing depends, for instance, very

the idea of regional network and cluster is not new [5].

much on innovative services like design, marketing

It is still very popular. e. g. although Germany started

and logistics as well as on product related after-sales

first policy measures to set up regional networks and

services and vice versa. More and more service

cluster in the late 90s, even today there is a significant

fi rms are manufacturing goods that build upon or

number of support programmes ongoing [6]. the same

are related to their service offerings or distribution

is for the most industrialized countries world-wide [6].

channels. But regional and industrial development

Within a network there are actors that interact, thereby

policies and tools still do not often take sufficient

contributing to the constitution of the cluster. Regional

account of these changes. service innovation is in

networks and cluster usually consist of companies,

fact a driver of growth and structural change across

research institutions, universities and other relevant

the whole economy. It helps to make the entire

actors in a given geographical space (Fig. 3).

economy more productive and provides fuel for innovation in other industries. It even has the potential to create new growth poles and lead markets that have a macro-economic impact [4].

Matured innovation policies today have a broad spectrum of innovation support measures in place that focus to strengthen innovability of individuals (e. g. better education, life-long learning, staff involvement in innovation projects, etc), companies (e. g. adopting organizational structured towards open innovations, implementation of innovation managements schemes, etc.) and networks (e. g .cluster development, involving companies in innovative networks, etc.).

Figure 3: Typical actors within networks and clusters

11

cHAPteR I.

It is comparable new that there is clear evidence

following process phases with the respective share of

that the ability of a regional network or cluster to

the network manager are shown in Figure 5. Interviews

deliver high economic performance often depends

and self-assessment conducted by the network

on the excellence of the network management [6].

managers confi rm that most responsibility is required

network and cluster excellence can, for example, be

at the beginning and at the end of the process of

expressed in terms of growth, added value provided,

innovation management. In the implementation

productivity and innovativeness of the network actors.

phase the network manager is least needed, since it

nowadays, there is no doubt that network and cluster

has to be implemented by the enterprises themselves.

management excellence matters, and the main

this curve repeats itself and/or overlaps with other

questions of scholars and practitioners refer to the

innovation management curves depending on the

ways of achieving it [6].

way the network is run.

one of the factors that is seen as essential for achieving networking and cluster excellence refers to high quality of the management. Figure 4 displays the correlation between the spectrum and quality of services delivered by a professional network or cluster management and the impact of the work of the network and cluster management organization on business activities of enterprises. the more services are provided (see e.g. the median value), the higher the impact on business activities of enterprises is.

Figure 5: Responsibility of network manager along the innovation chain [9].

CENTRES OF EXCELLENCE centres of excellences (coe) are structured, long term research or innovation oriented collaborations Figure 4: Effect of spectrum and intensity of services provided by network and cluster managements on business activities of enterprises [7]

in strategic important areas between academia, industry and the public sector. In general they aim to bridge the gap between industry and academia by providing a collective environment for academics,

Promoting open innovation arenas is a key task

industry and other innovation actors and creating

for network and cluster managers today. open

sufficient critical mass. centres of excellence can

Innovation is designed to enhance the innovation

provide multiple activities, like pooling of knowledge,

potential of enterprises by obtaining external and

creation of new knowledge by performing different

broadening internal know-how because it is based

types of research, training and dissemination of

on cooperation with others. network managers are

knowledge, and networking of the main stakeholders

therefore responsible for sharing out know-how to the

and key players involved (from academia, industry

target persons, enabling them to learn from each

or innovation actors from the policy or government

other. the relevance of networks for enterprises’

levels). the primary characteristic of a coe, that

innovative capacity can be traced to the capacity of

may differ from case to case, is whether or not the

network structures to encourage innovation, because

main focus is on research as a knowledge basis

networks within companies too are conducive to

for innovation (in other words: turning money into

a better exchange of know-how [8]. With regard to

knowledge) or the goal is to produce innovations as a

work intensity and responsibility of a centralized or

result of centre activities (i.e. turning knowledge into

overall innovation management in a network, the

money).

12

chapter I.

Nowadays, CoEs are a very popular tool to bring

structures is desirable. However, in some cases,

together industry and academia, and enable more

relevant cornerstones are imposed by the funding

sustainable innovations. The rationale is that such CoE,

programme or agency behind the CoE.

provided they are adequately staffed with researchers and fully technologically equipped, can offer innovation-related services according to their clients’ needs. The clients are considered to be enterprises

CONCLUSION

that need support in creating innovations. Thus,

Nature is innovation is continuously changing, even in

they can offer R&D, if appropriate, but also support

the future. It will have a significant impact on industry

enterprises in how to better innovate new products

and academia. Consequently, all actors of the triple

and technologies.

helix - industry, academia and policy – have to better

Strategic objectives of a CoE depend on the technological domain a CoE is active in and on the specific demands of the clients. The objectives could be [10]: • interconnection of scientific excellence, visions of the industrial partners and available capacities in the respective country, • generating internationally comparable knowledge in the respective fields, and its transfer into applied

cooperate in the future and have to jointly design new tools to promote innovations. Regional networks and Centers of Excellence are, as shown in the text, promising tools to strengthening innovability in industry and academia. However, this will be not enough for the future. Smart innovation policies, taking regional strengths and potential better in mind than in the past, could be a promising way to increase competitiveness of the regional actors. The Smart Specialization approach could become a powerful tool, provided it is seriously turned into practice.

practices • scientific excellence, interdisciplinarity of research and development, facilitating conditions for technological breakthroughs for industrial partners • producing highly trained staff at under and

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Expanding the Innovation Horizon – The Global CEO Study 2006. IBM Global Business Services, pp

reaching global levels and creating new high-

21 – 23, 2006

tech companies. Raising competitiveness of large, medium and small enterprises; creating new

Godin B., The Linear Model of Innovation, in

3.

The Smart Guide to Service Innovation, European

employment positions and high-tech and spin-off

Commission, Brussels, ISBN 978-92-79-26011-7, 2011,

companies

available http://ec.europa.eu/enterprise/policies/ sme/regional-sme-policies, 2011.

However, although so many CoEs exist all over the world, some of them are more successful than others.

Among others, the basis for success of a CoE is a

4.

Meeting the challenge of Europe 2020: The

well-functioning governance structure, aimed at

transformative power of service innovation,

permitting smooth processes inside the CoE and,

Available http://www.europe-innova.eu/web/

at the same time, involving the main stake holders

guest/innovation-in-services/expert-panel/

in the (strategic) decision-making processes. The

publications, 2011

governance and management of a CoE requires infrastructures and management procedures that

5.

differ substantially from those in universities, research organisations and industry. However, these CoE structures and procedures share numerous interfaces with the corresponding organisational environment and requirements of these institutions.

Expert Panel on Service Innovation in the EU,

Porter M. E., The competitive advantage of nations, New York: The Free Press, 1990

6.

Lämmer-Gamp Th, Meier zu Köcker G., Christensen Th, Clusters are Individuals. New Findings from the European Cluster Management and Cluster Program Benchmarking, Danish Ministry of

Therefore, when setting up a CoE, a very careful

Science, Technology and Innovation, ISBN: 978-87-

design of the management and governance

92776-22-8, Copenhagen/Berlin, pp 20 – 30, 2012

13

chapter I.

7.

Kind S., Meier zu Köcker G., Developing Successful Creative and Cultural Cluster - Measuring their

M., Bruns M., Petersen M., Vogt M., Innovation management in Networks- Sharing knowledge,

Tanja Mühlhans (eds.), Senate Department for

gaining new markets“, available:

Economic,Technology and Research; Initiative

https://www.kompetenznetze.de/

Projekt Zukunft, Berlin, Available: http://www.iit-

veroeffentlichung, 2012 10. Dermastia M., „Polimat Center of Excellence –

Bruns M., Inter-organisational innovation

Strategies and objectives“, available:

processes in the agrifood industry: An approach

http://en.polimat.si/1/co-polimat/strategic-goals.

to improving management support services

aspx, 2013

applied to the meat industry”, Ph.D. dissertation, Dept. Hohe Landwirtschaftliche Fakultät der Rheinischen Friedrich-Wilhelms-Universität, University Bonn, Germany, 2011

14

Müller L., Meier zu Köcker G., Bovenschulte

outcomes and impact with new framework tools,

berlin.de, 2011 8.

9.

chapter II.

Chapter II. IDENTIFICATION OF NEEDS

Value-driven Engineering Austen BioInnovation

T

Institute in Akron, USA

global competitiveness. Specifically, the increasing commitment and ability of

Stephen D. Fening and Frank L. Douglas

fdouglas@abiakron.org

he culmination of a number of factors has moved the U.S. from the ‘Rising Storm’ to the ‘perfect storm’. The current economic crisis coupled with increased healthcare costs, global competition for talent, and increased

investment in innovation by emerging countries have the potential to erode U.S. China, India, and Brazil to compete globally for talent, ideas, and infrastructure deployment in many areas of science and technology is evident in their increased investment in R&D. Within 10 years, China’s R&D investment as a percentage of GDP is expected to reach that of the U.S. [1]. The economic crises in the U.S. and Europe also present a relative competitive advantage to these three countries for global talent and ideas to create the next generation of technologies. Moreover, although 32 of 46 medical technology companies with $1 billion in revenue are presently based in the U.S. [2], many have simultaneously reduced U.S.-based R&D as they build up their presence abroad in response to increasing R&D investment, attractive corporate tax rates, competitive wage structures, and growing markets in these emerging countries. For example, in August 2011, General Electric (GE) moved its X-ray leadership team from the U.S. to China and has increased its R&D for products specific for the rural Chinese market in recent years [3]. In 2007, Stryker opened its Global Technology Center in Gurgao, India [4]. Furthermore, with U.S. health expenditures as a percentage of GDP projected to reach 19.3% by 2019 [5], innovation of new processes and products that further improve outcomes and reduce costs of health care is critical.

This ‘perfect storm’ is increasing the call for a renewed focus on value. This focus on value is not new; various institutions have employed several definitions of value as a solution to an unmet problem (i.e., high costs). However, each has approached “value” differently. For example, the Department of Defense has used Value Engineering (VE) to improve their ability to obtain cost-effective services and products since 1954 [6]. As required by Public Law (PL) 104-106, which was signed

by President Clinton in 1996, each executive agency in the U.S. Government must establish and maintain cost-effective VE procedures and processes [7]. In VE, value is defined as the ratio of function to life cycle cost. Similarly, the former Governor and Secretary of the U.S. Department of Health & Human Services, Michael Leavitt, articulated the need for value in the healthcare industry as a means to drive down

15

chapter III.

costs by simultaneously increasing competition and

that could be used in emerging markets as well as in

empowering the consumer [8]. In his speech, “Building

the event of a potential influenza pandemic. The first

a Value-based Health Care System”, Secy. Leavitt

OneBreath Ventilator is based on a novel platform

described value as a function of quality and cost.

technology, which represents a significant departure

More recently, in an approach to obtaining value in

from current designs, with the clinical need driving

healthcare delivery, Michael Porter defined value

specifications. It is less expensive to purchase (~$1000)

around the customer, focusing on health outcomes

and maintain, easier to use and more durable than

relative to the total costs associated with the full

existing ventilators while being as accurate. Other

cycle of care for a particular condition [9]. Because

examples include the Zio™ Patch, a long-term cardiac

maintaining good health is less costly than managing

rhythm monitor that provides continuous monitoring

poor health, Porter reasoned that a value-based

for up-to-14 days, GE’s VScan portable ultrasound,

system will contain healthcare costs [10].

as well as an inexpensive, point-of-care technology

None of the aforementioned approaches to value should be confused with frugal engineering, which focuses on understanding customer needs and delivering products and services to match those needs, in the most economical manner. Frugal engineering often entails the creation of devices or solutions that meet the needs of the end-user without the ‘bells and whistles’ or standard features. Examples of products developed using frugal engineering include Tata Motors’ Nano, a low-cost automobile, and Nokia’s 1100 cell phone. Historically, practitioners of frugal engineering reverse engineered existing products to identify the critical components needed to deliver the intended benefit and design solutions that contain primarily those critical components. The solutions are typically focused on a single market and often have limited applicability across other markets.

The key components of the value-driven engineering include the following: clinical utility for the end-user, reduced complexity for the end-user, and reduced costs to the healthcare system. Best quality of materials, processes, and functionality as a sine qua

that uses paper, as known as the “Lab-on-a-Chip” from Diagnostics for All [14]. Furthermore, elements of value-driven engineering (i.e., clinical utility, low cost, reduced complexity to the end-user) are evident in some of The Scientist’s annual Top 10 Innovations 2011, which includes LUCAS, an inexpensive, pocket-sized microscope, the PCR in a Pouch FilmArray system that simultaneously detects multiple pathogens in a shorter period of time without requiring a trained technician as well as the Mini MRI [15].

GE has several products which underscore the principles of value-driven engineering. For example, GE’s $1000 handheld electrocardiogram (ECG) machine, which was developed in an Indian R&D lab for use in rural India, improved clinical utility by enabling greater patient access, reduced cost to the healthcare system by improving compliance and lowing the cost of the device, and finally made the device less complex to operate than a typical ECG system. Another example from GE is the Vscan portable ultrasound which offers similar benefits. While these devices were designed for markets like India,

non, as is patient-centricity. Reduced costs to the

because they address all three domains of value-

healthcare system is important because it implies that

driven engineering, they have broad market appeal

the device might actually cost more than predicate

and are now being sold in other markets, including

devices. Furthermore, decreased complexity to the

the United States. Furthermore, GE announced in May

end-user permits its use by downstream providers,

2009 that it will invest $3 billion to create 100 similar

dramatically reduces non-device costs, improves

healthcare innovations aimed at lowering costs,

patient compliance, and most importantly for target

increasing access, and improving quality [12].

markets – improves patient access.

A group of science leaders from academia, industry,

By simultaneously focusing on clinical utility, reduced

and government has been assembled to serve as

cost to system, and simplicity to end user, value-driven

a steering committee for the initiative. This group

engineering products have broad market reach and

released a White Paper, entitled “Value-driven

appeal to the patient, provider, and to the healthcare

Engineering and U.S. Global Competitiveness” on

system. Optimizing these elements throughout the

June 17, 2011 [13]. After receiving much attention, a

design, development and manufacturing phases

conference was held in Akron, OH in 2012 with over

remains a challenge. Fortunately, devices that fulfill

300 attendees from all over the Unites States. The

these characteristics already exist. For example,

initiative is gaining ground internationally as well,

OneBreath, Inc. has developed a low-cost ventilator

serving as a bedrock for a recent collaboration

16

chapter III.

between the Austen BioInnovation Institute and

NationalHealthExpendData/downloads/proj2009.

Slovenia’s Center of Excellence in Polymer and

pdf

Materials Technology. This partnership uses the principles of value-driven engineering to screen areas

6.

Systems Engineering. Value Engineering: A

of innovation.

Across the Austen BioInnovation Institute Partnership, Value-Driven Engineering has become part of the

Guidebook of Best Practices and Tools, 2011 7.

in screening technologies for commercialization. Most

8.

2008 in Washington, DC, The Prologue Series

fully exhibit value-driven engineering: they improve

“Building a Value-based Health Care System.”

clinical utility to the end user, reduce costs to the complex in use than their predicate.

Leavitt, MO Secretary, U.S. Department of Health and Human Services, Speech given on April 23,

of the products which have come out of the institute

healthcare system, and the use of these devices is less

National Defense Authorization Act for Fiscal Year 1996, PUBLIC LAW 104–106—FEB. 10, 1996

culture. It is a key competency throughout our entrepreneur education initiatives and is a key metric

Office of Deputy Assistant Secretary of Defense,

9.

Porter, ME. What Is Value in Health Care? N Engl J Med 2010; 363:2477-2481

10. Porter, ME. A strategy for health care reform –

CONCLUSIONS Value-driven Engineering offers tremendous potential to serve as a tool to bring healthcare costs in line with quality outcomes, something which is both needed in the US as well as critical to bolster our ability to remain globally competitive. It is an approach to developing new products that are in line with a set of core, defining value-driven Engineering principles: (1) clinical utility - driven by patient-centricity in demand, design, use and function, (2) reduced complexity - in the function of the device to the end user, and (3) cost savings and cost efficiency across the health system. Cost is not the cost of a device, but rather the cost of the treatment of a disease. In value-driven Engineering, best quality of materials, processes, and functionality as sine qua non, as is patient-centricity.

toward a value-based system. N Engl J Med 2009; 361:109-112 11. Sehgal V, Dehoff K, Panneer G. The importance of frugal engineering. strategy+business 2010; 59:1-5.

12. http://www.ge.com/news/our_viewpoints/ healthcare_reform.html 13. http://www.abiakron.org/Data/Sites/1/pdf/ abiawhitepaper6-14-11.pdf 14. The One-Cent Solution: How a chemist and a doctor found a much cheaper way to diagnose disease. Popsci http://www.popsci.com/ bown/2011/innovator 15. http://the-scientist.com/2012/01/01/top-teninnovations-2011/

REFERENCES 1.

United Nations Educational, Scientific and Cultural Organization and PWC

2.

2010 Standard & Poor Industry Surveys: Healthcare – Products and Supplies

3.

http://www.reuters.com/article/2011/07/25/uschina-ge-healthcare-idUSTRE76O3U520110725

4.

http://www.mpo-mag.com/news/2007/03/27/ stryker_opens_global_r%2526d_centre_for_ medical_technology_in_gurgao

5.

Centers for Medicare & Medicaid Services, Office of the Actuary. National Health Expenditure Projections 2009-2019 https://www.cms.gov/

17

chapter III.

Chapter III. BIOPOLYMER SCIENCE AND TECHNOLOGY

Medical Devices and Biomaterials for Mauritius Sujata K. Bhatia

INTRODUCTION

Harvard University,

A new class of implantable medical materials, constructed from naturally-derived

School of Engineering and Applied Sciences, USA sbhatia@seas.harvard.edu

and renewably-sourced polymers, is poised to transform clinical medicine by providing materials with improved performance and versatility. Biopolymers can empower developing countries to leverage their own agricultural capabilities to contribute to novel medical technologies. Biochemical engineering and biomedical engineering, both of which fall under the broad category of biological engineering, are being brought to bear for the development of bio-based materials as biomedical materials. Toward the goal of a sustainable bio-economy, research in biochemical engineering is increasingly devoted to the development of renewably sourced materials, such as bio-polymers and bio-composites derived from biomass and obtained from agricultural resources or microbial production. At the same time, innovators in biomedical engineering are seeking novel materials for implantable medical devices which will be optimally compatible with the human body. Such optimized materials will have properties of biocompatibility and mechanical tunability that maximize the clinical benefits of the implant. A natural intersect exists between these two areas of emerging research: naturally sourced polymers may be ideal for the design of new biomedical devices, as such polymers can effectively interface with human cells and tissues. This paper will discuss the evolving field of bio-based materials as biomedical implants, and describe success stories.

DEFINING BIO-BASED MATERIALS Bio-based materials, also known as biopolymers or bio-derived materials, are engineering materials made from substances which are derived in whole or in part from living matter. Bio-based materials are classified into three main categories based on their origin and production [1]: • Bio-based materials can be directly extracted or removed from biomass.

Examples of these biopolymers include polysaccharides such as starch, cellulose,

18

chapter III.

alginates, carrageenan, pectin, dextran, chitin, and

characterization must include mechanical

chitosan. Additional examples include proteins such

properties, physical and chemical properties,

as casein, glutein, whey, silk proteins, soy proteins,

biological properties, shelf stability, and usability. The

and corn proteins.

surgical target will determine the precise technical

• Bio-based materials can be produced via classical chemical synthesis using bio-based monomers from renewable agricultural resources. A prime example

specifications for a given biomaterial. Clinician input is indispensable to the design process; surgeon needs and patient needs must guide the material design.

is poly-lactic acid, a biopolyester that is made from

As the prevalence of chronic conditions such as

lactic acid monomers. The monomers themselves

cardiovascular disease, diabetes, arthritis, and

can be derived from fermentation of agricultural

neurodegenerative diseases rises in the global

carbohydrate feedstocks, such as corn starch.

community, there will be an even greater need for

• Bio-based materials can be produced directly by microorganisms. The main example of a biopolymer derived from microbial production is the polyhydroxyalkanoate family of polymers.

Additional examples include xanthan and bacterial cellulose.

innovative biomaterials that interact optimally with the human body. Bio-based polymers are increasingly being recognized as biocompatible materials which can re-create natural, functional, bioactive structures in the human body. Bio-based materials are characterized by both tissue compatibility and versatility, and have demonstrated success in wound

Biopolymers are an intuitive choice for biomedical

closure, tissue repair, and tissue engineering. Such

applications such as wound healing and tissue

materials carry a great deal of hope for lightening the

engineering, given that bio-based materials are

heavy burden of disease and death worldwide.

constructed from naturally-derived materials, and may be expected to be friendly to biological tissues.

Moreover, bio-based materials possess tunable chemical, physical, and mechanical properties, so that these materials can be readily constructed to match the native properties of a variety of target

SUCCESS STORIES: CARBOHYDRATES FOR CLOSING WOUNDS

tissues, and ultimately be implanted in the human

One successful example of the utility of bio-derived

body to enable re-growth of cells and tissues.

materials for biomedical applications is that of polysaccharide (carbohydrate)-based tissue glues.

REQUIREMENTS OF BIOMEDICAL MATERIALS

There is a pressing need in clinical medicine for biomaterials that reliably close surgical wounds.

Despite refinements in suturing and stapling techniques for wound closure, physicians continue

A biomedical material may be defined as “a

to struggle with the problem of leakage from internal

nonviable material used in a medical device,

wounds; a great demand exists for tissue adhesives

intended to interact with biological systems” [2]. An

to augment or replace sutures and staples for internal

essential characteristic of biomedical materials is

wound repair. While tissue glues based on synthetic

biocompatibility, the ability to function appropriately

chemicals such as cyanoacrylates or glutaraldehydes

in the human body to produce the desired clinical

have been developed and commercialized,

outcome, without causing adverse effects. Biomedical

such adhesives have limited clinical usage, due

materials must meet stringent performance requirements: novel biomedical materials must have sufficient physical, biological, and mechanical similarity to the natural physiological environment.

In addition, the biomedical material construct and any degradation products must be non-toxic and

to biocompatibility and performance problems including inflammation and tissue damage. A family of hydrogel tissue adhesives, based on the natural polysaccharide dextran, has thus been developed to overcome the limitations of existing tissue glues.

non-inflammatory. The implanted material must not

Dextran is a high molecular-mass polysaccharide

interfere with wound healing nor induce a foreign

synthesized from sucrose, and composed of chains of

body response. New biomedical materials must

D-glucose units [3]; the molecule was first discovered

be assessed throughout the development process,

by Louis Pasteur as a microbial product in wine [4].

to ensure suitability for medical applications;

The polysaccharide is manufactured by lactic-acid

19

chapter III.

bacteria, including Leuconostoc mesenteroides,

ophthalmology, just to name a few of the numerous

Streptococcus mutans, and Lactobacillus brevis, as

medical applications.

well as Aerobacter capsulatum. Dextran already has a long history of clinical use as a plasma volume expander, for the treatment of circulatory shock.

Dextran-based tissue glues have been created by reacting dextran aldehyde with multi-arm polyethylene glycol-amines; the two components form a crosslinked hydrogel [5]. This system crosslinks on wet tissues, cures rapidly in less than one minute at room temperature, adheres to moist tissue, and degrades hydrolytically. The polysaccharide-based tissue adhesive is also advantageous in that it is free of blood products, so there is no potential for viral transmission. In vitro testing of the dextranbased tissue glues with clinically relevant cell lines reveals that these adhesives are non-cytotoxic to connective tissue fibroblasts, and do not elicit release of inflammatory mediators (in contrast, commercial tissue adhesives based on cyanoacrylate are highly cytotoxic to connective tissue fibroblasts).

The biocompatibility, biodegradability, adhesion properties, and convenience of polysaccharidebased tissue glues make these adhesives an effective system for treating a wide variety of wounds. The

SUCCESS STORIES: SOY FOR SECURING BONE Bio-based materials have demonstrated potential not only for wound closure in soft tissues, but also for repair of bony defects. Damages and defects in bone can result from traumatic events or surgical procedures; when the defect reaches a critical size, the bone is unable to spontaneously regenerate, and bone fillers are required to support new bone formation. Bone reconstruction requires materials that are easy to handle, biodegradable, non-cytotoxic, non-immunogenic, and capable of inducing bony regeneration. Currently there are no commercial bone fillers that meet all of these technical requirements.

Soybeans can be a source of naturally bioactive implantable materials; soybeans contain bioactive phytoestrogens that can induce differentiation of osteoblasts (bone-forming cells). An innovative class of bioactive fillers based on soybeans has thus been created for bony reconstruction.

foundation chemistry enables fine-tuning of sealant

Soybean-based biomaterials are synthesized by

properties, including cure rate, degradation rate, and

simple thermosetting of defatted soybean flour; the

swelling, to meet surgeon needs for specific clinical

soybean-based biomaterial is ductile and can be

targets.

processed into films, membranes, porous scaffolds,

In preclinical studies, dextran-based tissue adhesives have demonstrated success in closing a variety of surgical incisions and wounds, including vascular graft closures; aortic graft closures; aortic punctures; aortic anastomosis; graft punctures; cardiac punctures; coronary artery incisions; intestinal anastomosis; hernia patch attachment; liver lobectomy; and splenectomy [6]. The sealant is well-tolerated in shortterm and long-term studies; the sealant remains on

and granules for various surgical applications [9].

Alternatively, soybean-based formulations can be obtained by extraction of a fraction enriched in the main soy components, resulting in a soft hydrogel. The ductility of soybean-based biomaterials enables these fillers to be readily adapted to the site of implantation.

The biomaterials absorb water, with the swollen material assuming a rubbery consistency, and the materials degrade in a controlled fashion.

the target site with no injury to adjacent tissues. In

Soybean-based biomaterial granules have been

addition, the polysaccharide-based tissue adhesive

shown to be bioactive in vitro; the soybean-based

is successful in sealing corneal incisions, and is non-

granules reduce the activity of inflammatory

toxic to corneal cells [7]. The tissue adhesive is strongly

monocytes and macrophages; reduce the activity

bonding and sufficiently robust that 1-2 microliters of

of osteoclasts (bone-removing cells); and increase

the dextran-based tissue glue is capable of sealing

the activity of osteoblasts (bone-forming cells). These

a clear corneal incision through the first five days of

results suggest that upon implantation, the soybean-

healing [8]. Tissue glues based on naturally-derived

based bone filler may be able to reduce chronic

polysaccharides therefore represent a promising

inflammation while simultaneously promoting bone

platform for sealing and healing soft tissues. The

regeneration by stimulating bone cells. The soybean-

polysaccharide-based materials will find clinical utility

based materials additionally induce calcification

in general surgery, cardiothoracic surgery, vascular

of bone noduli. Importantly, the soybean-based

surgery, emergency medicine, trauma surgery, and

bone filler is cost-effective to produce, relative to

20

chapter III.

commercial bone fillers [10]. Unlike existing bone

for centuries [15]; fibers composed of the silk fibroin

fillers which are loaded with expensive growth

protein are biocompatible, and slowly degrade over

factors, soybean-based bone fillers do not require the

several weeks in vivo. Silk fibers are therefore long-term

addition of exogenous growth factors for bioactivity.

degradable biomaterials with excellent mechanical

Soybean-based bone fillers have been evaluated in pre-clinical rabbit models of bony defect repair, and the fillers have shown efficacy in inducing bone formation in vivo over 8 weeks of implantation [11].

properties. The fibers can slowly and predictably transfer a load-bearing burden to nascent biological tissues [16], making silk an ideal platform for tissue engineering.

Treatment with soybean-based granules produces

Silk hydrogels have been prepared from aqueous

bone repair and healing, with progressively maturing

solutions of silk protein via sonication-induced gelation

structural features of bone, as well as cellular features

[17]. One particular silk hydrogel has been formulated

superior to those obtained from healing in a non-

to yield mechanical properties similar to those of

treated bony defect. Moreover, in a rabbit model of

cartilage; these scaffolds can support the proliferation

defects of cancellous bone (the spongy inner layer

of chondrocytes, and may be utilized for cartilage

of bone that protects bone marrow), treatment with

tissue engineering [18]. Silk nanofibers can also be

soybean-based fillers resulted in significantly higher

manufactured by aqueous-based electrospinning

outer bone formation and microhardness at 24 weeks

of silk and silk/poly(ethylene oxide) blends [19].

than did treatment with a commercial synthetic

Electrospun silk protein scaffolds have been evaluated

bone filler [12]. Soybean-based bone fillers may be suitable for orthopedic, maxillofacial, and periodontal

for vascular tissue engineering, and can support the growth of human aortic endothelial cells and human

surgeries.

coronary artery smooth muscle cells. Moreover,

Further, soybean-based biomaterials have been

of interconnecting networks of capillary tubes [20].

combined with gelatin and hydroxyapatite

Electrospun silk nanofibers can be shaped into tubular

composites to create injectable foamed bone

materials with sufficient mechanical strength to

cements [13]. The soy/gelatin/hydroxyapatite foam

withstand physiological blood pressures, and may find

contains interconnected pores after injection; this

utility as tissue-engineered vascular grafts.

porosity allows the infiltration of osteoblast cells into the scaffold. The composite foam favors osteoblast adhesion and growth; some cells establish a very close contact with the material surface. Because soybased bone cements are injectable, these cements could be utilized for bone regeneration in a minimally invasive fashion. Clinical applications for these novel foamed cements include vertebroplasty and kyphoplasty for the treatment of vertebral fractures, and implant fixation procedures.

electrospun silk scaffolds stimulate the formation

Silk scaffolds have additionally demonstrated potential for bone tissue engineering and ligament tissue engineering. Towards bone tissue engineering, silk scaffolds have been chemically modified with covalently bound RGD peptide sequences. These scaffolds promote the attachment of human bone marrow-derived mesenchymal stem cells, and demonstrate mineralization and the formation of organized bonelike trabeculae [21]. For ligament tissue engineering, silk-fiber matrices have been designed to match the mechanical requirements of

SUCCESS STORIES: SILK FOR SCAFFOLDING TISSUES

a native human anterior cruciate ligament, including

Just as polysaccharide-based glues may transform

and differentiation of adult human progenitor bone

soft tissue closure, and soybean-based fillers may

marrow stem cells [22]. Silk-based biomaterials have

advance bone repair, silk-based biomaterials

even demonstrated the ability to support neurite

have the potential to enhance tissue engineering.

outgrowth from dorsal root ganglia neurons, and

Silk protein fibers are produced by both silkworms

silk conduits are capable of bridging short gaps in

and spiders, and are characterized by a unique

severed nerves by enabling axonal regeneration

combination of high strength and extensibility [14].

[23]. Further, in a rat model of peripheral nerve

The toughness of silk fibers is superior to that of any

injury, silk conduit implantation allows nerve repair

commercially available, synthetic high-performance

and functional recovery. Given the outstanding

fiber. Silk fibers have been in clinical use as sutures

mechanical properties and aqueous processability

fatigue performance.

These matrices support attachment, expansion,

21

chapter III.

of silk fibers, as well as the ability of silk scaffolds to

empower developing countries to leverage their

support numerous cellular populations including stem

own agricultural capabilities to enter the biomedical

cells, silk-based biomaterials may eventually find

revolution. Biopolymer scientists can therefore

applications for tissue engineering in every organ

consider themselves as not only part of the research

system of the body.

and development team, but also as part of the patient care team.

FUTURE DIRECTIONS Bio-based materials, derived from natural polymers including polysaccharides and proteins, are poised to

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transform clinical medicine by supplying biomedical

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success stories of polysaccharide-based tissue glues

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New polymers, synthesized using monomers obtained

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from agricultural resources, are one avenue for

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future innovation. For instance, films and plastics composed of corn-derived 1,3-propanediol have

Ratner, B.D., et al., Biomaterials Science: An

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been demonstrated to be non-cytotoxic and

butyrous fermentation,” Bulletin de la Société

non-inflammatory to clinically relevant cell lines

Chimique de Paris, 11, pp. 30-31 (1861).

[24]; such materials may be readily adapted for biomedical implants. Agricultural resources such as

5. Bhatia, S.K., et al., “Interactions of polysaccharide-based tissue adhesives with

soy, kenaf, flax, and cellulose may also provide useful

clinically relevant macrophage and fibroblast cell

starting materials for implantable medical devices.

lines,” Biotechnology Letters, 29, pp. 1645-1649

Moreover, additional polymers derived from microbial

(Nov. 2007).

production are under exploration. As an example, polyhydroxyalkanoates are naturally-occurring polyesters that are synthesized by most bacteria,

6. Bhatia, S.K., et al., “Polysaccharide-based tissue adhesives for closure of surgical wounds,”

and these materials are being investigated for tissue

Proceedings of the 2008 American Institute

engineering [25] and targeted drug delivery [26]. With

of Chemical Engineers Annual Meeting,

progressive efforts of biopolymer scientists in these

Philadelphia, PA (Nov. 16-20, 2008).

areas, physicians and surgeons will soon see novel biopolymers for clinical applications.

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Bhatia, S.K., et al., “Polysaccharide-based tissue adhesives for sealing corneal incisions,” Current

Moreover, naturally-derived polymers can allow

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developing nations to join in the biomedical revolution in ways that were not previously possible

8. Chenault, H.K., et al., “Sealing and healing of clear corneal incisions with an improved dextran

[27]. Agriculture tends to play a significant role in the

aldehyde-PEG amine tissue adhesive,” Current

economies of developing nations, particularly those

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in tropical or semi-tropical regions. Taking the relative strengths of these economies, and in particular the strengths of individuals at the community level, a new “technology” that makes use of materials derived from these crop products seems to be a viable option worth investigation. Bio-based polymers can

22

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Santin, M., et al., “A new class of bioactive and biodegradable soybean-based bone fillers,” Biomacromolecules, 8, pp. 2706-2711 (Sep. 2007).

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chapter III.

biomaterials: preparation, properties and tissue

23. Huang, W., et al., “Regenerative potential of silk

regeneration potential,” Expert Reviews in

conduits in repair of peripheral nerve injury in

Medical Devices, 5, pp. 349-358 (May 2008).

adult rats,” Biomaterials, 33, pp. 59-71 (January

11. Merolli, A., et al., “A degradable soybean-based biomaterial used effectively as a bone filler in vivo

2012).

24. Bhatia, S.K., and J.V. Kurian, “Biological

in a rabbit,” Biomedical Materials, 5, pp. 15008

characterization of Sorona polymer from corn-

(Feb. 2010).

derived 1,3-propanediol,” Biotechnology Letters,

12. Giavaresi, G., et al., “Bone regeneration potential of a soybean-based filler: experimental study in

30, pp. 619-623 (April 2008).

25. Hoefer, P., “Activation of polyhydroxyalkanoates:

a rabbit cancellous bone defects,” Journal of

functionalization and modification,” Frontiers in

Materials Science: Materials in Medicine, 21, pp.

Bioscience, 15, p. 93-121 (January 2010).

615-626 (Feb. 2010).

13. Perut, F., et al., “Novel soybean/gelatine-based

26. Grage, K., et al., “Bacterial polyhydroxyalkanoate granules: biogenesis, structure, and potential use

bioactive and injectable hydroxyapatite foam:

as nano-/micro-beads in biotechnological and

material properties and cell response,” Acta

biomedical applications,” Biomacromolecules,

Biomaterialia, 7, pp. 1780-1787 (April 2011).

10, pp. 660-669 (April 2009).

14. Omenetto, F.G., and D.L. Kaplan, “New

27. Fatunde, O.A., and S.K. Bhatia, “Health care in

opportunities for an ancient material,” Science,

the developing world: embracing a new definition

329, pp. 528-531 (July 30, 2010).

of medical technology to include biomaterials,”

15. Moy, R.L., et al., “Commonly used suture materials in skin surgery,” American Family Physician, 44, pp.

Ethics in Biology, Engineering, and Medicine, 2, pp. 353-364 (2011).

2123-2128 (Dec. 1991).

16. Horan, R.L., et al., “In vitro degradation of silk fibroin,” Biomaterials, 26, pp. 3385-3393 (June 2005).

17. Wang, X., et al., “Sonication-induced gelation of silk fibroin for cell encapsulation,” Biomaterials, 29, pp. 1054-1064 (March 2008).

18. Chao, P.-H.G., et al., “Silk hydrogel for cartilage tissue engineering,” Journal of Biomedical Materials Research B: Applied Biomaterials, 95, pp. 84-90 (October 2010).

19. Jin, H.-J., et al., “Electrospinning Bombyx mori silk with poly(ethylene oxide),” Biomacromolecules, 3, pp. 1233-1239 (August 2002).

20. Zhang, X., et al., “In vitro evaluation of electrospun silk fibroin scaffolds for vascular cell growth,” Biomaterials, 29, pp. 2217-2227 (May 2008).

21. Meinel, L., et al., “Engineering bone-like tissue in vitro using human bone marrow stem cells and silk scaffolds,” Journal of Biomedical Materials Research A, 71, pp. 25-34 (October 2004).

22. Altman, G.H., et al., “Silk matrix for tissue engineered anterior cruciate ligaments,” Biomaterials, 23, pp. 4131-4141 (October 2002).

23

chapter III.

Potential of Biopolymers Andrej KrĹžan National Institute of Chemistry, Laboratory for Polymer Chemistry and Technology, Slovenia andrej.krzan@ki.si

INTRODUCTION Polymers play a crucial role in today’s world. As a distinct material group they directly or indirectly enable the existence of major technologies, such as transportation, electronics, healthcare, construction, sports etc., and have penetrated virtually every human activity. Due to the extreme range of properties that make polymers and plastics applicable to so many requirements and needs, their efficient production based on fossil derivatives, and the ease of processing, they represent a true technological revolution that has contributed to an availability of high quality products for people all around the world and a general rise in the quality of life.

This amazing achievement of polymers and plastics is reflected in the rise of global production from less than 2 million tons in the 1950s to quantities that are now approaching 300 million tons (285 million tons in 2011, according to Plastics Europe).

This is even more amazing considering that the first man-made polymers and plastics were not produced until the second half of the 19 th century and that the first proper glint into the structural nature of polymers as macromolecules was given by Herman Staudinger only in 1920.

Contrary to common belief, consistently held more or less all around the world, polymers and plastics are materials that raise our overall sustainability. They are produced in a very efficient way, albeit from non-renewable fossil resources, but moreover they allow countless applications that contribute to energy and resource savings. For example, all objective analyses of the universally vilified plastic bag show that a plastic bag is more resource efficient than its alternatives. When we try to avoid the single use bag the best option is again a plastic bag, however a durable one, made from either film or fiber. Plastic packaging allows high resource efficiency through preservation of products, especially food, that require a large energy and resource investment in their production. Polymers in coatings protect structures from corrosion, lowering maintenance and replacement needs. Polymers play a key role in thermal insulation by directly lowering the energy requirements for heating or cooling. Use of plastics in the construction of vehicles reduces their mass and thus lowers fuel consumption. Plastics are essentially indispensable in modern medical care where they, for example, provide safe and sterile single-use medical implements that can preserve health or even save lives.

ENVIRONMENTAL CHALLENGES OF POLYMERS AND PLASTICS Despite the many benefits of polymers and plastics, they of course still cause an environmental burden. As a result of new research and our improved understanding, we now recognize two particular issues as most important for raising the sustainability of plastics: one is the fact that plastics are made from non-renewable fossil resources, and the second is the threat that scattered waste plastics pose to the environment.

24

chapter III.

The fact that plastics are made from non-renewable

A partial answer to the issue may be found also in

(fossil) resources is inherently unsustainable, since

biodegradable plastics. Their chemical structure

the original fossil resource cannot be replenished

allows microrganisms to degrade these materials into

and is destined to grow increasingly scarce in the

harmless natural products such as carbon dioxide,

future. A more fundamental problem with the use of

water and biomass. However, the degradation must

fossil resources is that we are very rapidly transferring

take place under appropriate conditions (industrial

fossilized carbon into the environment and ultimately

composting, home composting, marine environments,

into the atmosphere, where its concentration in the

etc.) for which the material has been designed.

form of carbon dioxide and other problematic carbon compounds is rising above all historically known levels. This is considered to be a cause of climatealtering processes. A method to address this issue is to

BIOPOLYMERS AND BIOPLASTICS

produce plastics on the basis of renewable resources,

Biopolymers is a loosely defined term. In the narrow

such as biomass. If production is carried out in an

meaning it stands for natural polymers, such as

efficient way, without the need for excessive energy

cellulose, proteins, chitin, DNA, etc., however it is often

inputs and avoiding other negative effects on the

used in more generally to signify polymers and plastics

environment (deforestation, over-fertilization, etc.) and society (especially raising the cost of food and feed), bio-based plastics could in principle lower our dependence on fossil resources and reduce green house gas emissions, thus making plastics much more sustainable.

The second issue is less connected to altering how plastics are made but is rather dependent on how we as consumers use plastics and what we do with them post-consumption. Namely, due to the ever increasing amount of plastics produced and their wide use, increasing amounts are released into the environment. This takes place through intentional or unintentional practices that will be difficult to eliminate entirely. Once in nature plastics degrade quite slowly, so they can be considered a stable pollutant. This is especially important in aqueous environments that allow uninhibited transport to the floating plastic waste. The fact that plastics are accumulating in the seas and oceans first became apparent in the Pacific Ocean, where a large area polluted by an accumulation of plastics often referred to as the Pacific Gyre was discovered. Subsequent studies have shown that plastics can be found in virtually all marine environments, raising concern about potential long-term effects. Plastics have a direct effect on marine life, causing entanglement or death through ingestion, however there is also the hidden effect of microplastics, which have the ability to concentrate persistent organic pollutants and potentially enter the food chain. The most important method to combat this uncontrolled spread of plastics in the environment is

that involve biological resources and processes either in their formation or degradation. A related term adopted by European Bioplastics, the largest industrial association in the field, is Bioplastics, which is defined as biobased and/or biodegradable plastics.

It is important to understand that the two categories (biobased and biodegradable) of plastics are not synonymous. Biobased plastics made from renewable resources may be biodegradable or not, and biodegradable plastics may be derived from biomass, fossil resources or a combination of both resources. The reason for this is that biodegradability depends solely on the chemical structure of the polymers involved and does not depend on the source of the raw material from which they are made. Of course, biobased polymers can be biobased (normally expressed by the percentage of biobased carbon content) in the entire range of 1–100%. The same is not true for biodegradable plastics. In order to be accepted as biodegradable they must be biologically convertible in their entirety (100%). Furthermore, biodegradability is a generic description that must be defined in terms of the conditions under which it takes place and a time limit within which it takes place. To be exact we must therefore refer to specific degradation conditions, such as composting (home or industrial), or degradation in soil or water. In order to avoid any possible misunderstanding it is prudent to use the established national or international standards (specifications and methods) that define in a detailed way how appropriate tests should be performed and how results should be interpreted.

to improve waste management practices. Recycling

The following examples of bioplastics will illustrate

in particular is a preferred approach since it has been

that a fair number are both 100% biobased and

clearly shown that it can recover the highest portion

biodegradable, although all other combinations

of the energy and resources invested in the material.

mentioned also exist.

25

chapter III.

EXAMPLES OF BIOPLASTICS

Polyhydroxyalkanoates (PHA)

There are a number of bioplastics that are currently

PHAs are a diverse group of fully natural thermoplastic

commercially available. It is particularly interesting to look at the principles through which they area made, since they depend on different raw materials and various combinations of physicochemical and biological processing. The selected examples presented below serve to illustrate these approaches.

Thermoplastic starch (TPS) A natural carbohydrate polymer – starch is used as material and energy storage in many plants. In

polyesters, produced by native microorganisms as a material and energy storage. PHA are composed from B-hydroxyacids, so a number of polymers can be prepared. The most common are poly-3hydroxybutyrate (PHB), poly-4-hydroxybutyrate, and poly-3-hydroxy butyrate-co-3- hydroxy valerate (PHBV). Production is based on the fermentation of sugars or other substrates directly to the polyester. PHA is formed into granules inside the microorganism. At the optimal time, the fermentation is stopped and the polyester is extracted from the biomass.

nature, starch is made of a mixture of amylose and amylopectin in crystalline granular form; this can then be turned into a processable thermoplastic mass through mixing with plasticizers such as water or glycols at elevated temperatures. TPS is normally blended with biodegradable polyesters to improve its material properties and processing properties. TPS is mainly used for film blowing and is commonly used for packaging, as well as for bags for organic waste collection.

Aliphatic and aliphatic-aromatic polyesters A whole group of biodegradable (compostable) aliphatic and aliphatic-aromatic polyesters have been synthesized from a mixture of renewable and non-renewable starting materials. The most widely used examples are polybutylene adipat terephthalate (PBAT), polybutylene adipate succinate (PBAS), and polycaprolactone (PCL), although a number of other variants are known. These materials are produced

TPS preparation starts with a natural polymer

in a fully chemical (non-bio) way and are entirely

whose polymer structure is preserved during

or at least in large part made from non-renewable

physicochemical processing. The most commonly

based monomers. The production method allows

used sources of starch are corn/maize, potatoes, and

a fine-tuning of composition and thus properties

cassava.

leading to high quality materials. All of these materials are defined as biodegradable under industrial

Polylactide (a.k.a. Polylactic acid, PLA)

composting conditions.

PLA is chemically synthesized from a natural

A recent trend in the plastics industry is to produce

compound, lactic acid, obtained through the fermentation of sugars that are commonly prepared from starch. Lactic acid is first oligomerized and then transformed into a cyclic dimer of lactic acid, lactide, which is then polymerized through a ring opening polymerization process. The obtained PLA is a high quality material. Its thermal properties depend on the chirality of the lactic acid moieties. Common PLA grades are not suitable for use above its relatively low (approx. 60°C) glass transition temperature. The polymer biodegrades under industrial composting conditions but remains stable under home

exact equivalents of non-biobased conventional plastics from new biobased sources. This approach is based on new production methods for basic chemicals and monomers from biomass, which can be used in conventional polymer and plastic production. Two notable examples of this approach are bio-polyethylene (bioPE) and biopolyethyleneterephthalate (bioPET), although many others are becoming available. These bioplastics that are entering into an already developed market are expected to experience very fast growth over the next few years.

composting conditions.

PLA is based on the fermentation of sugars to produce

Bio polyethylene (bioPE)

lactic acid – the monomer that is then converted to

BioPE production is based on ethanol production

PLA in a number of chemical steps. The production

through the fermentation of sugars. Ethanol is then

depends on using a natural compound as a

dehydrated to ethylene, which undergoes the

monomer, although the polymer itself is not a natural

conventional polymerization process to produce

form.

polyethylene. The product is technically equivalent

26

cHAPteR III.

to Pe produced from fossil resources. the process

and oils. All of these can also be used for food and

will likely be improved by the use of new second-

feed production, which opens ethical issues and food

generation sources such as cellulose. However, the

supply questions. At the current production levels the

fermentation from sugar to ethanol is a relatively

demand for raw materials for plastics production is

wasteful step in terms of carbon utilization. BioPe is

not critical; however, as the production of bioplastics

commercially available.

is expected to grow at rates close 15% annually this may soon become an issue. this prospect leads to

Bio polyethyleneterephthalate (bioPET)

the need to develop so-called second-generation renewable resources. these are less convenient to use

currently, commercial bioPet uses biobased ethylene

and include ligno-cellulosic resources such as wood,

glycol in the polymerization of Pet to produce 30%

waste streams from agricultural and food production,

biobased carbon Pet. the production of biobased

and other waste biomass. With the change in biomass

terephthalic acid, the other co-monomer used

importance it is also expected that production will,

in Pet synthesis, is currently in a late development

at least in part, move to locations where abundant

stage and will become available shortly. After this

biomass can be produced. so in addition to a

is implemented, fully 100% biobased bioPet will

technological change, a geographic shift can be

become available. the production of bio terephthalic

expected as well. In the current analyses, south-east

acid is based on new processes for the production

Asia and north and south America fi gure as important

of BtX (benzene, toluene, xylene) aromatics from

biomass sources, whereas certain other equally fertile

bioresources. P-Xylene is then easily transformed in

regions such as Africa seem to be missing from these

terephthalic acid. the advent of biobased aromatics

predictions.

will allow these products to enter into many other polymer production streams, such as PU, Ps, PA, etc., thus providing the biobased polymer portfolio with a new expansion route.

Isosorbide based polymers In addition to making known plastics biobased, a number of new biobased polymers are also being introduced to the market. An example illustrating this trend is the isosorbide monomer developed by Roquette. Isosorbide is produced from starch and glucose. the cyclic monomer with two hydroxyl groups is suitable to be incorporated into polyesters to form a Pet analogue material (PeIt) or into polycarbonates.

Isosorbide:

countries and regions that are signifi cant producers of sugar are in an excellent position to capitalize on the current situation in which simple sugars are the preferred substrate while cellulose based production is still under development. conversion of sugars into biopolymers may be seized as an opportunity to enter the biopolymer area, especially since it allows the production and marketing of a biopolymer product that has a higher added value compared to sugar. the production can also take advantage of side products from sugar production, such as molasses and vinasse. As the technology of cellulose conversion to simple sugars is developed, early adopters should be able to switch their biopolymer production to use cellulosic residues such as bagasse, which is now normally burned for energy production. the development, however, is quickly shifting in the direction of biorefi neries that will integrate a fully biobased production of chemicals, (polymer) materials, and energy in a highly efficient way.

CONCLUSIONS Plastics are a mature material class that is undergoing

BIOMASS SOURCES

a signifi cant evolutionary step, leading to higher

A key question related to biopolymers, and

polymeric nature of plastics that has led to their

particularly biobased plastics, is the type and source

great utility is now increasingly combined with nature

of biomass used in their production. currently, the raw

mimicking approaches that connect plastics to

materials used are almost exclusively starch, sugars

nature through the use of renewable raw materials

sustainability. the superb understanding of the

27

chapter III.

and structures that can seamlessly return to nature

4. Joint European Biorefinery vision for 2030,

after they are no longer needed. The intensification

Star-COLIBRI:

of biomass use still poses a number of questions that

www.star-colibri.eu/files/files/vision-web.pdf

is expected to lead to the emergence of a new integrated production of energy, chemicals, and

5. Plastic Waste in the Environment- report provided by the European Commission DG ENV:

materials.

http://www.plastice.org/links/plastic-waste-in-theenvironment/

SOURCES FOR FURTHER READING 1.

6. Leonardo da Vinci Program - Environmentally Degradable Plastics: www.biodeg.net/fichiers/ Training%20course%20(Eng).pdf

European Bioplastics: www.en.europeanbioplastics.org

2.

Biobased plastics: www.bioplastic-innovation.com

3.

Bio-based Chemicals, Value added Products from

7.

Tutorial on Biodegradable plastics: Principles of biodegradable plastics, the science, the hype and the misleading claims: http://www. assobioplastica.org/wp-content/uploads/2011/04/

Biorefineries: www.ieabioenergy.com/DownLoad.

Principles-of-BIODEGRADABLE-PLASTICS-the-

aspx?DocId=7314

science-the-hype-and-the-misleading-claims.pdf

28

chapter III.

A Brief on Research Projects at the ANDI Centre of Excellence for Biomedical and Biomaterials Research Archana Bhaw-Luximon Dhanjay Jhurry Theeshan Bahorun Vidushi Neergheen-Bhujun Sabrina D. Dyall ANDI CoE for Biomedical and Biomaterials Research a.luximon@uom.ac.mu

INTRODUCTION Founded in May 2011 as a Centre of research attached to the Faculty of Science of the University of Mauritius and designated Centre of Excellence in Oct 2011 by the African Network for Drugs and Diagnostics Innovation (ANDI), the Centre for Biomedical and Biomaterials Research (CBBR) set up its labs and offices in Dec 2011. CBBR focuses on research in the areas of: biomaterials and nanomedicine as well as on the development of value-added products from indigenous resources; biopharmaceuticals through evaluation of plant based foods/beverages and medicinal/endemic plants, and biological activity and molecular mechanisms of action involved in the prevention of disease conditions such as diabetes, cardiovascular diseases and cancers (Scheme 1). It has been working extensively with biopolymers and synthetic polymers and has recently patented its research findings on the use of sugar in the preparation of bio-amphiphilic polymers.

The centre provides training and research opportunities for Masters, PhDs and PostDocs in the above-mentioned areas. Through its well established regional and international linkages and network, CBBR positions itself as a bridge between University and Industry, a first of its kind in Mauritius. The establishment of the Centre for Biomedical and Biomaterials Research in Mauritius is to position the country in the knowledge economy and serve as a base for future developments. The Centre aims at acting as an interface between the University and the private sector both at national and international level. This short review presents the main research projects of the Biomaterials and Drug Delivery Unit as well as Biopharmaceutical Unit.

Scheme 1. Activities of CBBR

29

chapter III.

I. BIOMATERIALS AND DRUG DELIVERY Biomaterials (N. Goonoo, A. Bhaw-Luximon and D. Jhurry) The main objective of this thrust is to engineer polymer-based scaffolds for tissue engineering applications. Our group has reported on the successful elaboration of tailored diblock poly(ester-

Figure 1. Fluorescence microscopy images of HDFs on electrospun PDX/PMeDX scaffolds after (A) 1 and (B) 7 days (Scale bar = 200 mm)

ether) based copolymers and blends. Scaffolds for tissue engineering applications should be biocompatible, biodegradable, porous and possess appropriate mechanical properties. 1 Mimicking the PLGA family, we have reported on the synthesis of a dioxanone analogue namely D,L-3-methyl-1,4-dioxan-2-one (MeDX) and its copolymerization with dioxanone or blending with polydioxanone to produce either films or electrospun nanofibres, thus opening up new perspectives for these materials.

Drug Delivery (R. Jeetah, A. Veeren, Y. Jugdawa, A. Bhaw-Luximon, S. Dyall and D. Jhurry) The polymeric nanomicelles engineered by our group are summarized in Scheme 2. They consist of synthetic biodegradable polymers and bio-based polymers. Our group has focused on engineering novel amphiphilic block copolymers based on biodegradable synthetic polymers or biopolymers. Our novelty in this area has been the development of a novel class of

Random P(DX-co-MeDX) copolymers and diblock copolymers consisting of PCL and P(DX-coMeDX) have been synthesized by ring-opening polymerization of DX and MeDX and used to produce nanofibrous mats. The incorporation of MeDX units in the diblock copolymers influences both thermal properties and degradation kinetics through phase mixing of segments. Hydrolytic degradation studies 2

indicated that degradation occurred via bulk erosion and that the copolymers with higher mole % of MeDX degraded faster.

Blend films of semi-crystalline PDX and amorphous PMeDX have been prepared and their mechanical performance, thermal and degradation behavior investigated. Mechanical tests showed overall 3

reduced tensile properties of the blends with increasing weight percent of PMeDX due to a decrease in crystallinity.

Blends were immiscible over the whole range of

poly(ester-ether)s namely PEG-b-poly(Dioxanoneco-Methyldioxanone) copolymers. Adjustment of the dioxanone to methyldioxanone ratio gives a range of copolymers whose properties (physicochemical and biological) can be tuned to meet specific biomedical requirements. The efficacy of these copolymers to encapsulate and release anti-inflammatory or anti-TB drugs has been tested. Tuberculosis remains a major plague of the African continent. However, only a few studies report on the use of block copolymer micelles to encapsulate anti-TB drugs.

As a replacement of PEG, we have engineered poly(vinyl pyrrolidone)-b-PCL copolymers and used these systems to encapsulate and release two anti-TB drugs simultaneously.

We have also worked on a method to prepare sucrose-based polymers for use as drug nanocarriers.

This work has been filed as a patent which is presently being considered in SA.

compositions. Hydrolytic degradation studies showed that blend films with higher PMeDX content degraded faster. Electrospun nanofibrous mats of PDX/PMeDX blends were fabricated in varying weight ratios of the two components. 4 Fibres were significantly more thermally stable as compared to blend films. Electrospun PDX/PMeDX nanofibrous scaffolds had excellent biocompatibility as demonstrated by cell adhesion and proliferation (Figure 1).

30

Scheme 2. Drug Delivery Systems developed at CBBR

chapter III.

PEG-based systems

Polysaccharides-based systems

Amphiphilic PEG-poly(dioxanone-co-methyl

Natural polysaccharides

dioxanone) block copolymer nanomicelles, i.e. diblock MPEG-b-P(DX-co-MeDX) and triblock P(DXco-MeDX)-b-PEG-b-P(DX-co-MeDX) have been prepared and anti-tubercular drugs rifampicin, pyrazinamide and isoniazid were encapsulated within the micellar cores, either individually or in dual combination (Figure 2).5,6 We have established a scale to quantify drug-polymer interaction through the determination of their binding constants. This enables us predict drug release profiles and compare efficacy of different micellar systems.

We have reported on the grafting of polycaprolactone onto oligoagarose, obtained via controlled enzymatic degradation of native agarose8 and on the solution properties of these copolymers. We provide an assessment of their efficiency as nano drug carrier system using anti-inflammatory ketoprofen as model drug.9 Well-defined oligoagarose-g-polycaprolactone copolymers of varying PCL chain lengths have been synthesised using protection/deprotection chemistry.

The graft copolymers showed amphiphilic behaviour with spherical micelles in the size range 10 to 20 nm (Figure 4). The ketoprofen drug loading efficiency was shown to increase with the length of the hydrophobic PCL chain: 2% for PCL10 and 5.5% for PCL15. Sustained drug release was observed over a period of 72 h and was faster with shorter PCL chains.

Figure 2. Anti-TB drug loaded PEG-b-P(DX-co-MeDX)

PVP-based systems Amphiphilic polyvinylpyrrolidone-polycaprolactone diblock copolymer micelles were synthesized by Atom Transfer Radical Polymerization (ATRP). Rifampicin, pyrazinamide and isoniazid were encapsulated within micelle core independently or using a dual combination of drugs. While Rifampicin was found 7

to have the highest percentage loading and binding constant, Isoniazid had the highest drug release. The percentage drug loading and the sustained release profiles (Figure 3) indicate that our block copolymer systems have the potential to be used as anti-TB drug delivery systems.

Figure 4. Oligoagarose-g-polycaprolactone micelles

Synthetic polysaccharides Recently, a patent has been filed on the preparation of novel amphiphilic graft copolymers consisting of sucrose-ether polycondensates onto which biodegradable polymer chains such as polyesters, poly(ester-ether)s or polypeptides have been covalently grafted.10 This invention also includes the application of the prepared amphiphilic sucrose-ether polycondensates for drug or protein encapsulation and release.

II. BIOPHARMACEUTICAL UNIT Cancer chemopreventive actions of natural products: an insight into their molecular mechanisms (S. Ramsaha, T. Bholah, V. Neergheen-Bhujun, T. Bahorun) Figure 3. Release profiles and Binding constants of anti-TB drugs encapsulated using PVP-b-PCL

Our work on cancer research is currently focused on mushroom, medicinal plant and marine

31

chapter III.

(invertebrates, autotrophs and heterotrophs) extracts.

prevention for various metabolic ailments. In this

Mushrooms cultivated in Mauritius have so far been

line our recent work on pomegranate extracts

characterized for their phytochemical constituents

determining the antibacterial, anti-inflammatory and

and antioxidant activities using multi assay antioxidant

antioxidant potential of the non-edible parts of the

systems. An animal experimentation (using Balb/c

Mauritian cultivar of pomegranate clearly indicated

mice model) on the modulatory effects of these

their potency in functional health and in food

extracts on inflammation and hepatocarcinogenesis

applications.13

is ongoing in collaboration with CSJM Kanpur University. We recently demonstrated that N-methyl N-nitrosourea (MNU), a harmful industrial and environmental pollutant found in cigarette smoke and some processed foods, potentially activated inflammatory cytokines (IL-1β, IL-6) in hepatic cells with increased expression of NFκB which might be responsible for hepatocarcinogenesis in Balb/c mice.11 A work complementing existing data on established cancer traditional uses of A. marmelos emphasized the effect its hydroalcoholic extract has on the regulation of inflammatory cytokines (IL-1β, IL-6), antiinflammatory (IL-4), other tumor related genes (p53, Bcl-2) expression in MNU induced Balb/c mice (Figure 5). The immunomodulating effect of the leaf extract was examined in vivo and the study concluded by assessing the alteration of DNA bases and backbone structure by use of Laser Raman Spectroscopy.

12

Our group also demonstrated the potential applications of traditional plants and teas to improve lipid stability in food test systems14. Recent studies examining the oral and renoprotective activities of nutraceuticals have emphasized their supporting role in the management of diabetes and its complications.

In this context, our studies have encompassed the characterization of green tea phytochemicals, its effects on the energy metabolism of HEK-293 cell and on erythrocytes peroxidation. The antioxidant status and their alteration in Mauritian diabetic patients have been the subject of particular attention by our group.15,16 A randomized clinical trial has also been conducted to assess how FPP® could affect carbonyl accumulation in pre-diabetic patients. Our data illustrate the bioefficacy of FPP® green and black teas to modulate distinctive markers of diabetes mellitus and cardiovascular diseases in randomized Mauritian pre-diabetics, normal population and cohorts with ischemic heart diseases. 17-20 One significant finding of this work is that tea consumption has been shown for the first time to reduce the levels of C-reactive protein (CRP) and uric acid (Figure 6) indicators of the inflammation of the arteries that contributes to cardiovascular disease in high-risk patients.

Figure 5. A. marmelos hydroalcoholic extract modulates the regulation of inflammatory cytokines (IL-1β, IL-6), antiinflammatory (IL-4), other tumor related genes (p53, Bcl-2) expression in MNU induced Balb/c mice

Figure 6. Effect of black tea on Uric acid in ischaemic cardiac patients 20

Further data clearly suggest that 6 g of FPP® and 3 Oxidative stress, diabetes and cardiovascular diseases: Physiological, molecular and cellular effects of functional foods/dietary factors (N. Toolsee, J. Somanah, V. Neergheen-Bhujun, T. Bahorun)

cups of green tea day for a period of 14 weeks would improve the health and antioxidant statuses of prediabetic patients. Our data was highly supportive of the notion that supplementation with FPP can generally improve the antioxidant status of prediabetics, modulate oxidative stress and provide a

Phytochemicals as antioxidant prophylactic

significant level of protection to human erythrocytes

agents in functional foods display a sustainable

against free radical-induced hemolysis. 21

32

chapter III.

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to differential expression of IL-1β, IL-6 and Bcl2

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initiating hepato carcinogensis in Balb/c mice.

polymer-based scaffolds for bone and vascular

Preventive Medicine 2012, 54, S130

523 Goonoo N, Bhaw-Luximon A, Bowlin GL, Jhurry D. Diblock poly(ester)-poly(ester-ether) copolymers: I. Synthesis, Thermal Properties and Degradation Kinetics. Industrial and Engineering Chemistry Research 2012, 51, 12031 3.

Goonoo N, Bhaw-Luximon A, Rodriguez I, Bowlin GL, Jhurry D. Poly(ester-ether)s: I. Investigation of the properties of blend films of polydioxanone and poly(methyl dioxanone). (under review)

4. Goonoo N, Bhaw-Luximon A, Rodriguez I, Wesner

Kumar A. Effect of Aegle marmelos leaf extract on N-methyl N-nitrosourea induced hepatocarcinogensis in Balb/c mice.

Pharmaceutical Biology 2013, in press 13. Rummun N, Somanah J, Ramsaha S, Bahorun T, Neergheen-Bhujun V. Bioactivity of non-edible parts of Punica granatum L.: A potential source of functional ingredients. International Journal of Food Science 2013, in press 14. Ramsaha S, Aumjaud BE, Neergheen-Bhujun VS, Bahorun T. Polyphenolic Rich Traditional Plants

ether)s: II. Properties of electrospun nanofibres

and Teas Improve Lipid Stability in Food Test

from polydioxanone and poly(methyl dioxanone)

Systems. International Journal of Food Sciences

blends. (under review)

& Nutrition 2013, in press 15. Neergheen-Bhujun VS, Rosun H, Joonas N,

amphiphilic PEG-b-P(ester-ether) micelles

Bahorun T. Antioxidant status in Mauritian

as potential drug nanocarriers. Journal of

patients suffering from type II diabetes mellitus.

Nanoparticle Research 2012, 14, 1168

International Journal of Diabetes in Developing

6. Jeetah R, Bhaw-Luximon A, Jhurry D. Dual encapsulation and controlled delivery of antiTB drugs from PEG-block-Poly(ester-ether) nanomicelles. Journal of Nanopharmaceutics and Drug Delivery (under review).

Veeren A, Bhaw-Luximon A, Jhurry D. Polyvinylpyrrolidone-Polycaprolactone block copolymer micelles asnanocarriers of anti-TB drugs. European Polymer Journal 2013, in press 8. Bhaw-Luximon A, Jhurry D, Heerah Booluck M,

9.

12. Verma S, Bahorun T, Singh R K, Aruoma OI,

D, Schönherr H, Bowlin GL, Jhurry D. Poly(ester-

5. Jeetah R, Bhaw-Luximon A, Jhurry D. New

7.

Urea (MNU) induced altered DNA structure leads

Goonoo N, Bhaw-Luximon A, Bowlin GL, Jhurry

tissue engineering. Polymer International 2013, 62,

2.

11. Verma S, Bahorun T, Kumar A. N- methyl N-nitroso

Countries 2013, in press 16. Neergheen-Bhujun VS, Seenauth-Beesoo V, Joonas N, Aruoma OI, Bahorun T. Alterations in the antioxidant status of Mauritian patients suffering from diabetes mellitus and associated cardiovascular complications. (under review) 17. Somanah J, Aruoma OI, Gunness TK, Kowlessur S, Dambala V, Murad F, Googoolye K, Daus D, Indelicato J, Bourdon E, Bahorun T. Inhibitory effects of a fermented papaya preparation on

Correc G, Génicot S, Helbert W. Oligoagarose-

growth, hydrophobicity and acid production of

grafted-PCL: Synthesis and Characterization.

Streptococcus mutans, Streptococcus mitis and

Macromolecular Symposia 2009, 277(1), 14

Lactobacillus acidophilus:its implications in oral

Bhaw-Luximon A, Musharat Meeram L, Jugdawa Y, Helbert W, Jhurry D. Oligoagarose-g-polycaprolactone loaded nanoparticles for drug delivery applications.

Polymer Chemistry 2011, 2, 77

10. Jhurry D, Bhaw-Luximon A. A method of preparing

health improvement of diabetics. Food Science and Nutrition Preventive Medicine 2012, 54, S90 18. Toolsee NA, Aruoma OI, Gunness TK, Kowlessur S, Dambala V, Murad F, Googoolye K, Daus D, Indelicato J , Rondeau P, Bourdon E, Bahorun T. Effectiveness of green tea in a randomized

an amphiphilic graft copolymer, Patent filed No

human cohort: Relevance to diabetes and its

2012/00948 (SA)

complications. (under review)

33

chapter III.

19. Bahorun T, Luximon-Ramma A, Neergheen-

21. Somanah J, Bourdon E, Rondeau P, Bahorun T,

Bhujun VS, Gunness TK, Googoolye K, Auger

Aruoma OI. Relationship between fermented

C, Crozier A, Aruoma OI. Effects of a short term

papaya preparation supplementation,

supplementation of a fermented papaya

erythrocyte integrity and antioxidant status in pre-

preparation on biomarkers of diabetes mellitus in

diabetics. (under review)

a randomized Mauritian population. Preventive Medicine 2012, 54, S98 20. Bahorun T, Luximon-Ramma A, Gunness TK, Sookar D, Bhoyroo S, Jugessur R, Reebye D, Googoolye K, A. Crozier, Aruoma OI. Black tea reduces uric acid and C-reactive protein levels in humans susceptible to cardiovascular diseases. Toxicology 2010, 278, 68

34

cHAPteR III.

CHARACTERIZATION OF COMPLEx MACROMOLECULES Majda Žigon ce PoliMat, slovenia majda.zigon@polimat.si

INTRODUCTION Advanced polymeric materials are complex multi-component mixtures of macromolecules, varying in chemical composition, structure and chain length (Kilz and Pasch, 2000). since the properties of polymers strongly depend on their heterogeneity (Fig. 1), it is necessary to know not only the average composition,

Ema Žagar ce PoliMat, slovenia national Institute of chemistry, slovenia ema.zagar@ki.si

structure and length, but also the distribution of the named parameters. the average chemical composition, structure and functionality are usually determined by spectroscopic techniques (infrared (IR) spectroscopy, nuclear magnetic resonance (nMR), mass spectroscopy (Ms), UV-visible spectroscopy, etc.) and molecular weight distribution by size exclusion chromatography (sec), whereas thermal properties are determined by thermal techniques (differential scanning calorimetry (Dsc), thermogravimetric analysis (tGA), dynamic mechanical analysis (DMA), etc.) (Fig. 2, campbell and White 1991). Distributions of chemical composition, structure and chain length are usually measured by hyphenated techniques such as sec-MALs, sec-IR, Lc-Ms, Lc-sec, etc. (Kilz and Pasch, 2000).

In this contribution we present an overview of the listed techniques and typical applications for the characterization of complex macromolecules.

Figure 1. Schematic representation of the molecular heterogeneity of complex polymers

Figure 2. Instrumental techniques for the characterization of complex macromolecules

SPECTROSCOPIC TECHNIQUES For the determination of chemical structures, spectroscopic methods are the best suited, which include infrared (IR) spectroscopy, nuclear magnetic resonance (nMR), Raman spectroscopy, UV-vis spectrophotometry, mass spectrometry (Ms), gas or liquid chromatography coupled with mass spectrometry (Gc-Ms, Lc-Ms) or infrared spectroscopy (Gc-IR, Lc-IR), etc.

35

chapter III.

IR spectroscopy is one of the most widely used

desorption. The key to a successful MALDI analysis

spectroscopic methods in polymer laboratories.

depends primarily on uniformly mixing the matrix

Infrared radiation is a part of the electromagnetic

and the analyte. Samples are typically prepared

spectrum between the visible and microwave regions

in the concentration ratio of 1:1.04 analyte:matrix

(2.5–25 μm). Infrared radiation is absorbed by organic

in a suitable solvent such as water, acetone, or

molecules and converted into energy as molecular

tetrahydrofuran. A few microliters of this mixture is

vibration, either stretching or bending. Different

deposited onto a substrate and dried, and the solid

types of bonds, and thus different functional groups,

mixture is then placed into the mass spectrometer.

absorb infrared radiation of different wavelengths. An

It allows the analysis of biopolymers such as DNA,

IR spectrum is a plot of a wavenumber on the X-axis

proteins, peptides and sugars, as well as polymers,

to a percent transmittance or absorbance on the

dendrimers, and other macromolecules (Fig.3,

Y-axis (2). Uses of IR spectroscopy: (i) identification of

Pahovnik and Žagar, 2012).

a sample’s components via the fingerprint method by comparing sample and reference IR spectra; (ii) determination of average polymer composition; (iii) monitoring the reactions such as polymerization, cross-linking, degradation etc.; (IV) monitoring the formation and scission of H-bonds, etc.

NMR exploits the magnetic properties of nuclei, which are excited by an external magnetic field. Any atom with an odd mass or atomic number has a nuclear spin that can be studied by NMR. When the external magnetic field is applied the protons either align with (parallel) or against it (antiparallel). The stronger the applied magnetic field the greater the energy difference (ΔE) between the parallel and antiparallel states. An NMR signal is created once the radio wave

Figure 3. MALDI-TOF mass spectra of (a) poly(g-benzyl-Lglutamate) before (top) and after aminolysis (bottom) and (b) enlarged part of MALDI-TOF mass spectrum of poly(g-benzyl-Lglutamate) after aminolysis (Pahovnik, Žagar, 2012).

photons supplied match the ΔE of the nucleus. We can observe different nuclei, most often hydrogen and carbon (one-dimensional 1H and 13C NMR spectra) or interaction between the different cores of the same

THERMAL TECHNIQUES

or different types, usually by two-dimensional NMR

DSC: Differential Scanning Calorimetry measures

spectra. Samples can be analyzed in solution or in the

the temperatures and heat flows associated with

solid state.

transitions in materials as a function of time and

Applications of NMR spectroscopy for the analysis of polymers: (i) identification of components by comparing the sample and reference NMR spectra or tabulated values for different chemical groups; (ii) average composition of the sample; (iii)

temperature in a controlled atmosphere. These measurements provide qualitative and quantitative information about physical and chemical changes involving endothermic or exothermic processes or changes in heat capacity.

microstructure – configuration, tacticity, branching,

DSC is used to determine (i) glass transitions,

etc.; (iv) calculation of the number average molar

(ii) reaction kinetics, (iii) melting and boiling

mass, Mn; (v) study of hydrogen bonds formation; (vi)

temperatures, (iv) rate and degree of cure, (v)

monitoring of the reactions, e.g. polymerization; (vii)

crystallization time and temperature, (vi) degree

dynamics of polymer chains, etc.

of crystallinity, (vii) specific heat capacity, (viii)

MALDI – TOF: MALDI (matrix-assisted laser desorption/ ionization) generates high-mass ions by irradiating

enthalpies of both fusion and reactions, (ix) oxidative/ thermal stability, purity of material, etc.

a solid mixture of an analyte dissolved in a suitable

TGA: Thermogravimetric analysis measures the

matrix compound with a pulsed laser beam. As the

amount and rate of change in the weight of a

name implies, the laser pulse desorbs and indirectly

material as a function of temperature or time in a

ionizes the analyte molecules. A short-pulse (a

controlled atmosphere. Measurements are used

few nanoseconds) UV laser is typically used for

primarily to determine the composition of materials

36

cHAPteR III.

and to predict their thermal stability at temperatures

coupled with sec (sec-MALs), it gives absolute weight

up to 1000°c. tGA can characterize materials that

average molar mass (Mw) of polymers without a need

exhibit weight loss or gain due to decomposition,

for column calibration.

oxidation, or dehydration.

the usefulness of a hyphenated technique sec-

DMA: Dynamic mechanical analysis determines

MALs for the characterization of complex polymers

changes in sample properties resulting from

is refl ected in (i) dissolution on a molecular level,

changes in five experimental variables: temperature,

(ii) detection of non-size exclusion mechanisms, (iii)

time, frequency, force, and strain. DMA measures viscoelastic properties of materials: elastic modulus (storage modulus, e’), viscous modulus (loss modulus,

degradation studies (Fig. 4), (iv) monitoring the course of the reaction (Fig. 5), side reactions, etc.

e’’), damping coefficient (tan delta) as a function of

2D Lc: A reversed-phase liquid-adsorption

time, temperature, frequency or complex modulus,

chromatography (RP-LAc) can be combined with

transition points (alpha, beta, gamma), glass transition

sec into a two-dimensional liquid chromatographic

temperature, stress relaxation.

system (RP-Lc × sec) for simultaneous determination of polymer composition and molar mass distribution

SEPARATION TECHNIQUES

(Fig. 4, Šmigovec Ljubič, 2012).

one of the key issues in the characterization of polymers is how large the macromolecules are. size is expressed by the molar mass or degree of polymerization and hydrodynamic volume. Polymers are mixtures of macromolecules of different sizes because of the statistical nature of the polymerization processes. therefore, we are talking about the distribution of polymer molar mass. sec: With size exclusion chromatography (also gel permeation chromatography, GPc) we determine the distribution of molar mass or individual molar

Figure 4. Two-dimensional chromatographic separation of

mass averages much faster than by absolute

poly(styrene-co-isoprene) star copolymer, containing eleven

techniques such as osmometry, light scattering or ultracentrifugation. sec is based on separation

polyisoprene arms and schematic representation of the star copolymer (Šmigovec Ljubič, 2012)

according to the size of macromolecules or, more precisely, a hydrodynamic volume in the chosen solvent. separation is achieved via selective diff usion of molecules in the pores and out of the pores of

SUMMARY

column packing. small molecules pass through the

characterization of polymers is an important fi eld of

pores, medium molecules penetrate only part of

work for all those who are involved in the research and

the pores, while large molecules (larger than the

development of polymers and polymeric materials. An

pore size) traveling past the pores, are regarded

overview of spectroscopic, thermal and separation

as excluded. Larger molecules are eluted from the column faster than smaller ones. the determined molar masses are relative values and columns have

techniques, together with some typical examples will be presented.

to be calibrated by using polymer standards, such as polystyrene or poly(methyl methacrylate), with narrow dispersities in molar masses.

REFERENCES

sec-MALs: Light scattering (Ls) is a non-invasive

1.

Kilz, P., Pasch, H. coupled Liquid

technique for the characterization of synthetic

chromatographic techniques in Molecular

polymers, biopolymers and proteins in solution,

characterization. In: encyclopedia of Analytical

especially sensitive for species with high molar

chemistry, R.A. Meyers (ed.). John Wiley & sons

masses. It is an absolute technique and, when

Ltd, chichester: 7495–7543, 2000.

37

chapter III.

2.

3.

Campbell, D., White, J. R. Polymer

5. Šmigovec Ljubič, T., Rebolj, K., Pahovnik, D.,

Characterization, Physical Techniques. Chapman

Hadjichristidis, N., Žigon, M., Žagar, E. Utility of

&Hall, London: 1989, reprint 1991.

Chromatographic and Spectroscopic Techniques

Pahovnik D., Žagar E., unpublished results, 2012.

4. Šmigovec Ljubič, T., Pahovnik, D., Žagar, E., unpublished results, 2012.

38

for a Detailed Characterization of Poly(styreneb-isoprene) Miktoarm Star Copolymers with Complex Architectures. In: Macromolecules 45 (18): 7574−7582, 2012.

chapter III.

AGING CHARACTERIZATION OF POLYMERS Gernot Oreski1*, Kenneth Möller2, Gerald Pinter3 Polymer Competence

1

Center Leoben GmbH, Austria 2

SP Technical Research Institute of Sweden, Sweden 3

Science and Testing

of Polymers, University of Leoben, Austria

T

he aim of these investigations was to identify and evaluate appropriate degradation indicators for polymeric materials in order to characterize and assess the aging behavior and to predict the lifetime of materials. Therefore,

the influence of the relevant load parameters ultraviolet radiation, temperature and humidity on the degradation behavior of selected polymeric materials had to be determined. A test program concerning six accelerated aging tests was set up and a comprehensive study of five different polymer films and laminates materials and their degradation behavior was done. Therefore, the material properties and the aging behavior were characterized by infrared (IR) spectroscopy in attenuated total reflection mode (ATR), by UV/VIS spectroscopy by dynamical mechanical analysis (DMA) and by tensile tests.

Different degradation indicators were derived from the characterization methods and explicitly discussed. With the definition of reasonable end-of-life criteria, these degradation indicators serve as input data for lifetime modeling and assessment.

oreski@pccl.at

Experimental Five different polymer films and laminates were selected and investigated (Table 1). A test program concerning six accelerated artificial ageing tests was worked out. The aim of the accelerated ageing tests was to determine the influence of the relevant load parameters such as temperature, humidity and ultraviolet (UV) radiation on the degradation behavior of the selected materials.

The material properties and the aging behavior was characterized by infrared spectroscopy in attenuated total reflection mode (ATR), by UV/VIS spectroscopy, by differential scanning calorimetry (DSC), by dynamical mechanical analysis (DMA) and by tensile tests.

Table I: Investigated PV Encapsulation Materials

name

Composition

thickness

EVA

Ultra fast cure ethylene vinyl acetate

1085µm

Ionomer 1

Ethylene ionized acrylic acid copolymer

470µm

Ionomer 2

Two layer films, front: ethylene meth acrylic acid copolymer; back: ethylene acrylic acid/ acrylate terpolymer

600µm

TPT

PVF-PET-PVF multilayer film

170µm

Polyester

PET-PE multilayer film

310µm

39

chapter III.

Results and Discussion

Table II: Accelerated weathering tests.

Test no.

temp

humidity

UV

A comprehensive description of the degradation

1

85°C

85%RH

-

behavior of these materials has already been

2

65°C

85%RH

-

3

85°C

30%RH

-

different degradation indicators. These indicators

4

65°C

60%RH

60W/m²

were derived from the characterization methods and

5

85°C

26%RH

60W/m²

6

85°C

26%RH

120W/m²

reported elsewhere [1,2], so in the following this paper, concentrates on the derivation and evaluation of

explicitly discussed on one exemplary material.

In previous studies, it has been shown that tensile testing is the most versatile of the applied characterization methods in describing the aging

FTIR analysis was done in transmittance and in the attenuated total reflectance (ATR) mode, using a Spectrum GX FTIR spectrometer (PerkinElmer, Waltham, USA) with a Pike Miracle Micro-ATR device (Pike Technologies, Madison, USA). The ATR were measured spectra from 4000 to 650 cm-1. The UV/VIS/NIR measurements were carried out using a Lambda 950

behavior [3,4]. Strain-at-break and stress-at-break values are very sensitive to changes in molecular mass of the polymer and therefore sensitive to chemical aging. Furthermore, both values correspond well with material failure. Figure 1 shows exemplary stress-strain curves of TPT. Figure 1 shows exemplary stress-strain curves of TPT.

UV/Vis/NIR spectrometer with an integrating sphere to measure hemispherical and diffuse transmittance and reflectance spectra (PerkinElmer, Waltham, USA).

unaged aged

To characterize the thermo-mechanical properties DMA was done in tensile mode by using a DMA 861e (Mettler Toledo, Schwerzenbach, Swiss). A sinusoidal load was applied with a frequency of 1 Hz. The

stress [MPa]

Spectra were recorded from 250 to 2500nm.

x x

gauge length was 19.5mm. The scans were run in a temperature range from –60 to 150°C at a heating rate of 3K/min. Thermal analysis was carried out using

strain [%]

a Mettler DSC 821e instrument (Mettler Toledo GmbH, Schwerzenbach, CH). Thermograms were recorded under static air from –60 to 300 °C at a heating rate of 20 K/min. In a second run, to identify irreversible effects, samples were heated up from –60 to 150°C, cooled down back to 60°C and again heated up to 150°C. Melting point and melting enthalpy were evaluated according to ISO 11257-2 and ISO 11257-3.

The degree of crystallinity was determined as the ratio between the melting enthalpy of the sample and the melting enthalpy of the 100% crystalline polymer.

Tensile tests were carried out with a screw driven universal test machine (Zwick Z010 Allround-Line, Zwick, Ulm, D) at 23°C according to EN ISO 527-3. Rectangular specimens of 100mm in length and 15mm in width were cut prior to exposure using a device with fixed razor blades and rotating sample. The test speed was 50mm/min. From a total of at least five specimens for each test series, average numbers for elastic modulus

Figure 1: Stress-strain curve of an unaged and aged TPT.

Two different phenomena can be observed during accelerated aging of the investigated films. In the preyield and yield region at strains below 25%, changes in mechanical properties like elastic modulus or yield stress are predominantly associated with physical aging, i.e. changes in polymer morphology. Postyield effects like changes in the ultimate mechanical properties (strain-at-break, stress-at-break) are a very sensitive indicator for chemical aging, mostly changes in the molecular mass.

For all investigated polymer films, a clear influence of the stress factors UV radiation, temperature and humidity on the ultimate mechanical properties was observed (s. Figure 2).

(E), stress-at-break (S b) and strain-at-break (eb) were

After all tests, a significant decrease in strain-at-break

deduced.

and stress-at-break values was determined. The

40

chapter III.

embrittlement can be attributed to chemical aging.

increase in absorption and therefore yellowing can

Generally, UV radiation in combination with high

be found. The drop of hemispherical transmittance in

temperature (85°C) showed the biggest impact on the

the visual region can be assigned to the formation of

mechanical properties of all investigated materials,

chromophoric degradation products, mainly C=O and

as the strongest decrease in both, strain-at-break and

C=C double bonds, which absorb light in the region

stress-at-break values, has been measured after Tests 6.

between 250 and 450nm.

Usually, the transmittance values Th of a polymer film

strain-at-break [%]

200

Test 1 Test 4

Test 2 Test 5

Test 3 Test 6 TPT

150

the measured spectra with the AM1.5 solar spectral irradiance function between 300 and 2500nm.

Due to the observed simultaneous and competing

100

processes of yellowing and loss of UV absorber the calculated transmittance values exhibited only

50 0

for outdoor applications is calculated by weighting

small changes and remained rather constant after 5000h of aging. This behavior, which was observed 0

1000 2000 3000 4000 5000

aging time [h]

for all investigated transparent films, limits the use of hemispheric transmittance value weighted by AM1.5 over the whole solar range of wavelength as a

Figure 2: Strain-at-break values as a function of aging time for TPT.

degradation indicator. Therefore, a separation of the wavelength regions is necessary in order to obtain

UV/Vis/NIR spectroscopy in general is a powerful characterization technique, giving information on the optical properties like transmittance, reflectance, absorbance or scattering of materials. Next to the characterization of these basic properties, transmittance and reflectance spectra are a very sensitive indicator for chemical aging and the efficiency of UV absorbers and light stabilizers. Fig. 3 shows the hemispheric transmittance values of unaged and aged Ionomer 1 after exposure to 85°C and 85% RH.

appropriate degradation indicators.

The UV region between 295 and 400 nm serves as a measure of the efficiency of the UV absorber (UVA) and light stabilizers in the polymers. Furthermore the UVA retention can be assessed using the absorbance values A, which are given by (1)

A = − log(Th )

Figures 4 and 5 show the UV absorbance and visual aging time.

0.75

0.50

0.25

0.00

unaged aged 300

400

500

600

700

800

wavelength [nm] Figure 3: Hemispheric transmittance spectra of unaged and aged Ionomer 1.

After weathering for the transparent films in general

absorbance (295-400nm) [-]

hemispheric transmittance [-]

transmittance values of Ionomer 1 as a function of 1.00

1.50

Ionomer 1

1.25 1.00 0.75

Test 1 Test 2 Test 3 Test 4 Test 5 Test 6

0.50 0.25 0.00

0

1000 2000 3000 4000 5000

aging time [h] Figure 4: UV absorbance values of unaged and aged Ionomer 1.

two different processes have been observed. One the one hand, in the UV region below 400nm and

After all accelerated aging test depletion and loss

decrease in absorption due to loss of UV absorber

of UV absorber was observed (s. Fig. 4). Within the

was seen. On the other hand, in the visual region an

first 500h of accelerated aging, the depletion rate

41

chapter III.

is mainly influenced by the temperature. The tests at

by increase in OH region absorbance areas of FTIR

85°C (1,3,5,6) showed a significantly higher depletion

spectra, which are caused by formation of hydro

rate than the tests at 65°C (2,4). As shown in Fig. 5,

peroxide, carboxylic acid and alcohol groups.

a significant decrease in visual transmittance could

Therefore the region from 2200 to 3800 cm -1 was

be observed after Test 1. The same behavior but to a

integrated and the area due to CH2 absorbance

smaller amount was observed for the other two damp heat tests (Tests 2 and 3). Similarly to EVA or Ionomer

between 2700 and 3050 cm -1 was subtracted to obtain the OH absorbance area (s. Fig. 6).

2, only small changes in visual transmittance and little yellowing were observed after UV exposure. The transmittance values remained constant after 5000h at Test 4 (65°C / 60%RH / 60W/m² UV) and decreased

Th (400-800nm) [-]

0.950

absorbance [-]

slightly at Test 6 (85°C / 26%RH / 120W/m² UV).

Ionomer 1

0.925

CH peak

OH peak

0.900 0.875

Test 1 Test 2 Test 3 Test 4 Test 5 Test 6

0.850 0.825 0.800

0

4000

3500

3000

2500

wave number [cm-1] Figure 6: Hydroxyl and methylene stretching vibration region

1000 2000 3000 4000 5000

aging time [h]

At different exposure times t, the photo-degradation index is then given by

Figure 5: Visual transmittance values of unaged and aged Ionomer 1.

⎛ Area(OH ) ⎞ ⎛ Area(OH ) ⎞ − ⎜⎜ POI (t ) = ⎜⎜ ⎟⎟ ⎟⎟ ⎝ Area(CH ) ⎠ exp osed ⎝ Area(CH ) ⎠un exp osed

(2)

The above presented data confirm, the UV/Vis spectroscopy is a very useful tool for the definition of degradation indicators of polymers. Next to the basic solar transmittance and reflectance value the measured spectra are a very sensitive indicator for chemical aging and the efficiency of UV absorbers and light stabilizers.

Infrared (IR) spectroscopy is one of the oldest and most commonly used spectroscopic techniques for molecular level characterization of materials. It is perhaps the most important tool in the investigation of

The technique is very generic, i.e. it could be used for all kinds of polymers and no a priori information about the polymeric system would be needed.

The aging behavior, the degradation mechanisms and the changes in chemical structure of the investigated materials are well described in literature, especially for EVA and the Ionomers [3, 7, 8, 10 - 18]. But also the chemical degradation mechanisms for PET and the fluoropolymers PVF and PVDF for PV encapsulation

oxidation and photo-oxidation of polymeric materials.

purposes have been investigated in the past. [19].

In oxidation and photo-oxidation of polymers the

Figures 7 and 8 show the photo-oxidation indices for

degradation products contain hydroxyl (-OH) and

EVA and Polyester. For all polymers except for Polyester

carbonyl (-C=O) groups. The former forms alcohols,

a linear increase in degradation products was found.

while the latter form aldehydes, esters, ketones,

The strongest increase was seen after Test 6 at 85°C

carboxylic acids, etc. Carbonyl groups absorb

and with the double UV irradiance, the smallest after

infrared radiation effectively, which makes infrared

Test 4 at 65°C. It can be assumed, that UV radiation

spectroscopy an excellent tool to follow oxidative

in combination with high temperature levels has a

reactions [7,8]. In order to compare degradation

significant bigger influence on the degradation rate

caused by photo-oxidation, the Ford Motor Company

than temperature only. The humidity level seemed to

introduced a photo-oxidation index (POI) [9]. It

have less influence on the degradation rate or the

measures the accumulation of degradation products

POI.

42

chapter III.

Interestingly, in absolute numbers, for Ionomer 1

TPT laminate showed also a linear increase in POI,

the POI has a maximum value (after 2000h at Test

and like for the encapsulation materials UV radiation

6) of 0.08, whereas EVA and Ionomer 2 exhibit

in combination with high temperature levels

values around 0.4 after 2000 at Test 6. But UV/Vis/NIR

demonstrated the greatest impact on the materials,

spectroscopy and tensile tests showed at least for EVA

showing the fastest degradation rates. For TPT, the

a far better weathering stability and less chemical

POI values correspond better with the tensile test

aging. Also Ionomer 2 demonstrated a slightly better

results than the solar cell encapsulation materials, but

weathering stability, which is not reflected in the POI.

nevertheless some clear differences can be identified.

Whereas tensile test indicated only small influence of the irradiance dose on the mechanical properties, as after Tests 5 and 6 nearly the same strain-at-break

0.5

65°C / 60% RH / 1Sun 85°C / 26% RH / 1Sun 85°C / 26% RH / 2Sun EVA

POI [-]

0.4 0.3

absorbance spectra revealed a significant difference in POI between Test 5 and 6.

The most significant changes in IR spectra and the

0.2

highest POI values above 40 were found for the PET side of the Polyester laminate. Unlike for all the other

0.1 0.0

and stress-at-break values were measured, the ATR

investigated materials, the increase in POI was not 0

1000 2000 3000 4000 5000

aging time [h] Figure 7: Photo-oxidation index of EVA.

linear but exponential, leveling of in a plateau at longer aging times. But like before, the strongest increase was found after Test 6, the smallest after Test 4. The hydrolysis was also reflected in the tensile tests, where strong embrittlement and a significant decrease in ultimate mechanical properties,

60

65°C / 60% RH / 1Sun 85°C / 26% RH / 1Sun 85°C / 26% RH / 2Sun Polyester

50

POI [-]

40

especially after the UV tests was observed. But whereas after Test 6 the strain-at-break value has decreased to nearly 0 already after 125 of weathering, the POI value still increased strongly until 1000h.

30

In general it was found, that the degradation

20

rates obtained by IR spectroscopy with photooxidation index as degradation indicator, and

10 0

by tensile tests with strain-at-break and stress-at0

1000 2000 3000 4000 5000

aging time [h]

break cannot be correlated properly. Where for example photo-oxidation indices showed a steady linear increase, tensile tests showed no changes in

Figure 8: Photo-oxidation index of Polyester, PET side exposed

ultimate mechanical properties, like for EVA, or an

to UV.

extraordinary decrease, like for Polyester. Nevertheless infrared spectroscopy is a very important technique

These findings are in good agreement with an older study done at the PCCL in Leoben, where the intrinsic aging behavior of unstabilized EVA and ethylene acrylic acid copolymers (which have the same chemical composition as the ionomers) was investigated. For these materials, after UV exposure the

for the characterization of the aging behavior, which provides information of changes of the chemical structure due to weathering and of the amount of formed degradation products. But this information is not linked to material failure like the results obtained from tensile tests.

photo-degradation index showed a more or less linear

So far, mostly degradation indicators for chemical

increase in degradation products from the beginning.

aging processes, i.e. changes in the chemical structure

But no correlation between POI and the mechanical

of the polymer chain, have been discussed. But also

properties like strain-at-break or stress-at-break

physical aging has to be taken into account. It is well

values was found. Furthermore, unlike the ultimate

known for ethylene copolymers like EVA or ionomers,

mechanical properties, the photo-oxidation index

that storage at room temperature and exposure to

does not indicate material failure [18].

elevated temperatures result in changes in polymer

43

chapter III.

morphology and therefore to changes in the thermal

properties in the first 250h of damp heat testing with

and thermo-mechanical properties [20-24].

higher resolution. Exposure to UV radiation, especially

Although the elastic modulus of a material can also be determined by tensile tests, DMA is the preferable method. With DMA the elastic modulus can be

in combination with high temperature levels, leads to chain scission and therefore to a decrease in elastic modulus values (s. Fig. 10).

measured as a function of temperature. So, it not only gives information about the material stiffness, but also

4000

or softening of the material (s. Fig. 9).

Generally, physical aging is mainly induced by temperature. Introducing UV radiation as an additional stress factor complicates the analysis of the DMA curves, as two competing effects can be observed.

On the one hand, the absorbed radiation heats up the polymer, causing physical aging like described

E' (23°C) [MPa]

about thermal transitions like glass transition, melting 3000 2000 1000 0

85°C / 85% RH 65°C / 85% RH 85°C / 30% RH

0

TPT

1000 2000 3000 4000 5000

aging time [h]

before after damp heat testing. On the other hand, UV radiation also induces chain scission. The decrease in molecular mass result in decrease of the elastic modulus values, as primarily the interlamellar tie

Figure 10: Elastic modulus E’ (at 23°C) of Ionomer 2 as a function of aging time.

molecules and the entanglements in the amorphous zone, which are prominently responsible for the mechanical strength, are cleaved. But also after the damp heat tests with temperature and humidity load

Conclusion

only chemical aging by means of decrease of elastic

Based on these characterization methods, several

modulus can be observed.

degradation indicators for chemical and physical aging of the polymers were identified and evaluated.

Photo-degradation indices were determined from unaged aged

IR spectroscopy. This index is sensitive to chemical 0.6

damping factor [-]

elastic modulus [MPa]

1000 100

0.4

10

0.2

1

degradation and serves as a measure of the accumulation of degradation products, but is not indicating material failure. A better indicator was found in the solar optical properties obtained by UV/ Vis spectroscopy. By separating the ultraviolet and visible region, on the on hand the retention of UV absorber, which is important for the long time behavior

0.1 -50 -25

0

25

50

0.0 75 100

temperature [°C] Figure 9: Elastic modulus and damping factor of unaged and aged Ionomer 2 as a function of temperature.

of the material, could be assessed. On the other hand, solar transmittance in the visible range of wavelength is sensitive indicator for chemical aging, as it measures the formation of chromophoric degradation products.

Moreover, the transmittance is directly linked to module performance.

The obtained results indicate that DMA is a powerful

Strain-at-break and stress-at-break values gained

characterization technique in describing physical

from tensile tests proved to be very sensitive indicators

aging. In general, higher temperature levels during

for chemical aging. Both values correspond well with

exposure caused greater changes in thermal and

material failure. The elastic modulus, measured by

thermo-mechanical properties. The different humidity

DMA, was found to be the most appropriate indicator

levels had only small influence on changes in polymer

for physical aging. All films showed an increase of

morphology. This assumption is supported by the

elastic modulus values over the whole temperature

fact that for all films physical aging occurred within

range due to exposure at elevated temperatures. The

the first 250h of damp heat exposure and could be

changes in thermo-mechanical properties due not

confirmed by investigating the thermo-mechanical

correspond with material failure.

44

chapter III.

With the definition of reasonable end-of-life criteria,

15. M. Rodríguez-Vázquez, C.M. Liauw, N.S Allen,

these degradation indicators may serve as input data

M. Edge, E. Fontan, Polymer Degradation and

for lifetime modeling.

Stability 91 (2006) 154.

16. I.C. McNeill, M. Barbour, Journal of Analytical and Applied Pyrolysis 11 (1987) 163.

References 1.

17. I.C McNeill, A. Alston, Angewandte

G. Oreski, G.M. Wallner, Proceedings 24th European Photovoltaic Solar Energy Conference (2009) 4.AV.29

2.

G. Oreski, G.M. Wallner, Proceedings 24

1040.

20. R. Androsch, Polymer 40 (1999) 2805.

G.M. Wallner, C. Weigl, R. Leitgeb, R.W. Lang

21. M. Brogly, M. Nardin, J. Schultz, Journal of Applied

G. Oreski, G.M. Wallner, Biosystems Engineering 103 (2009) 489.

5.

A.W. Czanderna, F.J. Pern, Solar Energy Materials and Solar Cells 43 (1996) 101.

6.

19. G. Oreski, G.M. Wallner, Solar Energy 79 (2005) 612.

(2009) 4.AV.31

Polymer Degradation and Stability 85 (2004), 1065.

4.

18. G. Oreski, G.M. Wallner, Solar Energy 83 (2009)

th

European Photovoltaic Solar Energy Conference

3.

Makromolekulare Chemie 261/262 (1998) 157.

S. Krauter, R. Hanitsch, Solar Energy Materials and

Polymer Science 64 (1997) 1903.

22. Y. L. Loo, K. Wakabayashi, E. Huang, R.A., Register, B.S Hsiao Polymer 46 (2005) 5118.

23. Y. Tsujita, Journal of Applied Polymer Science 33 (1987) 1307.

24. L. Woo, Thermochimica Acta 243 (1994) 174.

Solar Cells 41/42 (1996) 557.

7.

N.S. Allen, M. Edge, M. Rodriguez, C.M. Liauw, E. Fontan, Polymer Degradation and Stability 88 (2001) 363.

8.

N.S. Allen, M. Edge, M. Rodriguez, C.M. Liauw, E. Fontan, Polymer Degradation and Stability 71 (2000) 1.

9.

J.L. Gerlock, C.A Smith, V.A Cooper, T.G Dusbiber, W.H. Weber, Polymer Degradation and Stability 97 (2003) 225.

10. B. Å. Sultan, E.Sörvik, Journal of Applied Polymer Science 43 (1991) 1737.

11. B. Å. Sultan, E.Sörvik, Journal of Applied Polymer Science 43 (1991) 1747.

12. B. Å. Sultan, E.Sörvik, Journal of Applied Polymer Science 43 (1991) 1761.

13. M.D. Kempe, G. Jorgensen, K.M. Terwilliger, T. McMahon, C.E. Kennedy, T.T Borek, Solar Energy Materials and Solar Cells 91 (2007) 315.

14. P. Klemchuk, M. Ezrin, G. Lavigne, W. Hollex, J. Gallica, S. Agro, S. Polymer Degradation and Stability 55 (1997) 347.

ACKNOWLEDGEMENTS The research work was performed at the Polymer Competence Center Leoben GmbH (PCCL, Austria) within EU-SP6 Integrated Project „PERFORMANCE“ in cooperation with the Chair of Materials Science and Testing of Plastics at the University of Leoben. The PCCL is funded by the Austrian Government and the State Governments of Styria and Upper Austria. Special thanks to G. Wallner, H. Mattausch, B. Hirschmann and A. Lovas for the support within the project.

45

chapter III.

Zinc Oxide: The Growth, Characterization and Preparation of Nanocomposites Zorica Crnjak Orel

INTRODUCTION

CE PoliMaT, Slovenia

With recent climate changes and the thinning of the ozone layer also UV radiation

zorica.crnjak-orel@polimat.si

dosage, including both UVB and UVA radiation, has greatly increased. (1). Even a relatively small increase in UV radiation has a substantial impact on human skin and eyes, on the biosphere, and the production of ground-level ozone. UV exposure also leads to the development of skin cancers, including melanomas, and perturbs the immune system of the body (2). Consequently, research has focused on the development of UV-protective materials such as UV-shielding materials suitable for applications such as UV-shielding windows, contact lenses, or glasses. Such materials can be made by incorporating suitable UV-absorbing materials into a transparent polymeric matrix.

Polymethacrylate-based nanocomposites with incorporated inorganic particles of uniform size and shape can be prepared, with the aim to produce efficient solid UV absorbers that are transparent for visible light, and possess improved resistance to thermal degradation in combination with enhanced mechanical properties. These materials should also possess robust mechanical properties, thermal stability and a prolonged durability.

As inorganic material, zinc oxide (ZnO) was proposed, which is environmentally friendly and represents one of the most technologically important and attractive semiconductor materials, and has become one of the important materials due to unique properties in near-UV region (3), electric conductivity and optical transparency. It thus shows great potential for applications in catalysis, optoelectronic devices, sensors, and photovoltaic. One-dimensional (1-D) ZnO nanostructure morphologies can be prepared in the form of wires, needles, tubes, fibres, columns, or helices. In addition, zinc oxide offers no toxicity problems compared to other NPs and is already used in pharmaceutical formulations. The antimicrobial activity of ZnO NPs has been well documented as well impact studies based on Escherichia coli bacteria in ultrafine ZnO nanoparticles colloidal medium (4). The preferences in using ZnO in amorphous polymeric matrices are in its high transparency in visible spectral region as well as its efficient protection against UV radiation at the wavelengths up to 375 nm at very low contents.

In this contribution, the preparation in batch reactors of non-agglomerated ZnO nano-to-submicrometer sized particles of different shapes will be presented. Some results will be presented on development of simple procedures for the production of transparent UV-protective nanocomposites, which still represents a great scientific challenge aiming at complete compatibility of ZnO nanoparticles with the polymeric matrix.

46

chapter III.

METHODS OF PREPARATION AND CHARACTERIZATION OF ZnO AND ZnO/PMMA PLATES

mechanism of ZnO particles was proposed (6,7). It

Preparation of ZnO NPs from solution (“solution route”)

(FE-SEM and HRTEM). The mechanism predicts the

is a low cost preparation method that has recently attracted a lot of interest due to the low temperature (room temperature up to 85-95 °C) particle growth. It is much more favorable for large-scale synthesis due to its very low energy consumption.

All experiments for the preparation of nano to submicro size ZnO particles were performed in reactor at controlled temperature. Schematic presentation of the preparation method is presented in Fig. 1.

The starting concentration of different zinc salts (nitrate, acetate, sulphate, chloride, perchlorate), type of solvents (water, different polyol and their mixtures), temperature, and pH influence the size and morphology of the final particles.

follows the “non-classical crystallization” concept as it was observed by the combining of the advanced insitu SAXS method and the ex-situ electron microscopy self-assembling of nanobuilding units (5-10 nm) into larger microstructures with prompt crystallization.

At the same time, the growth based on the direct attachment of ions from the solution also occurs in minor extension. Particle growth was also monitored indirectly via in-situ pH measurements (7).

Nucleation and growth of ZnO may be controlled by the local variation in the chemical potential of Zn2+ resulting from accumulation of OH─ at the gas-liquid interface. Polymer-assisted control of particle morphology and particle size of ZnO is another important synthetic route to prepare ZnO nanostructures. ZnO nanostructures of different morphologies (nanoparticles (NPs), nanorods, and flowerlike ZnO structures) were synthesized by controlling the content of a surfactant and the pH of the reaction mixture (6,9).

Possible mechanisms for the variation of morphology with synthesis parameters have been discussed (5).

The synthesized ZnO NPs were further used for the

Figure 1. Schematic presentation of the preparation of ZnO particles.

Crystalline fraction of synthesized powders was characterized by X ray diffraction (XRD), which confirm the formation of ZnO particles. Typical XRD diffractograms of ZnO particles is presented in Fig 2.

preparation of polymer/inorganic-material-based nanocomposites (14-16). Small particles typically aggregate, which negates any benefits of nanoscopic dimensions. Simply mixing NPs with most polymers usually leads to aggregation.

Miscibility of the inorganic particles and polymers is usually improved by introducing hydrophobic ligands such as alkyl silanes, oligomeric alkyl silicones, alkylphosphonic acid, hydroxy propyl methyl cellulose, fatty acids, amphiphilic statistical copolymer or block copolymers (diblock copolymers, double-hydrophilic block or grafted copolymers). A comprehensive investigation of the ZnO NPs with modified surfaces was performed using SEM, HR TEM and IR techniques.

The detailed analysis of presented micrographs in Fig. 3 show the formation of ZnO particles in dependence of the ratio water/ethylene glycol (EG). These particles were successfully covered with about 10 nm thick layer of SiO2. By FTIR analysis the formation of ZnO with

Figure 2. Typical XRD of ZnO particles (diffraction peaks position of ZnO corresponds to PDF 1-89-510).

band at about 455 cm-1 was additionally confirmed.

After the addition of TEOS (C8H20O4Si) the formation of SiO2 was also furthermore confirmed by the

The morphological properties of the obtained solids

presence of band at about 1100 cm-1 (8). Obtained

were characterized by other spectroscopic technique

particles were used for the preparation of ZnO/PMMA

such as IR, SEM and HRTEM (6-13). The assumed growth

plates.

47

chapter III.

Figure 4. UV-VIS spectra of PMMA and prepared ZnO/PMMA plates after addition of coated or non-coated ZnO

Polymethacrylate-based nanocomposites with incorporated inorganic particles of uniform size and shape were prepared (Fig. 4), with the aim to produce efficient UV absorbers that are transparent for visible light (14). As presented the prepared ZnO/ PMMA plates after the addition of coated or noncoated ZnO show excellent absorbance in the UV Figure 3. SEM micrographs of ZnO nanoparticles; (a) hexagonal

region with moderately transmittance in the VIS region

ZnO nanoparticles, (b) spherical nanoparticles and their

in comparison with pure PMMA. On the basis of the

corresponding HR TEM obtained after covering with TEOS.

results obtained on the laboratory scale the best achievements will be first scaled up in the laboratory

Most commonly, poly(methyl methacrylate) (PMMA)

setting and then, final products with the optimized

was used as the polymer phase due to its good

synthetic parameters will be transformed with

transparency and other favorable physical and

complete know-how to the pilot scale at facilities of

chemical properties.

industrial partners.

ZnO based/PMMA nanocomposites were tested on UV-shielding, thermal and other properties. We found that the presence of a very small quantity (0.04 wt. %) of ZnO based nanomaterial in the PMMA showed sufficient UV shielding (efficiently absorb UV light up to 370 nm) and at the same time good transparency in the visible-light region.

According to TEM, homogeneous dispersion of

CONCLUSIONS A Low temperature solution phase preparation method was successfully used for synthesis of the ZnO particles. The main results of our work show that the growth and morphology of the ZnO particles was controlled by changing the ratio of water/EG that serves as the medium for the preparation of ZnO.

ZnO particles in the amorphous PMMA matrix

New and improved properties of ZnO/ PMMA

was achieved. Thermal stability of the ZnO/PMMA

nanocomposites such as UV-shielding, mechanical

nanocomposites is considerably improved, even at

strength, thermal stability, and durability were

very low ZnO contents, and increased with increasing

achieved by using ZnO NPs as the only additive.

ZnO content. The onset of ZnO/PMMA decomposition

The analysis of the effects of ZnO NPs on the long-term

shifts for 20 - 40 째C to higher temperatures as

behaviour of PMMA confirmed the higher temperature

compared to pure PMMA (16).

stability for about 20-40째C when ZnO was added.

48

chapter III.

REFERENCES 1.

Ries, G., Heller, W., Puchta, H., Sandermann, H., Seidlitz, H.K., Hohn, B. Elevated UV-B radiation reduces genome stability in plants. Nature 406: 98-101, 2000.

2.

Brash, D.E. Sunlight and the onset of skin cancer.

Trends Genet. 13: 410-404, 1997.

3.

Yu, H., Zhang, Z., Han, X., Hao, X. and Zhu, F. A General Low-Temperature Route for Large-Scale Fabrication of Highly Oriented ZnO Nanorod/ Nanotube Arrays. J. Am. Chem. Soc. 127: 2378-238, 2005.

4. Brayner, R., Ferrari-Iliou, R., Brivois, N., Djediat, S., Benedetti, M. F., Fiévet, F. Toxicological impact studies based on Escherichia coli bacteria in ultrafine ZnO nanoparticles colloidal medium.

Nano Lett. 6: 866-870, 2006.

5. Pal, U., Santiago, P. Controlling the morphology of ZnO nanostructures in a low-temperature hydrothermal process. J. Phys. Chem. B. 109: 1531715321, 2005.

6. Bitenc, M., Orel, Z. O. Synthesis and characterization of crystalline hexagonal bipods of zinc oxide. Mater. res. Bull. 44: 381-387, 2009.

7.

Bitenc, M., Podbršček, P., Dubček, P., Bernstorff, D., Dražić, G., Orel, B., Orel, Z. O. The growth mechanism of zinc oxide and hydrozincite: a study using electron microscopies and in situ SAXS. CrystEngComm 14: 3080-3088, 2012.

8. Podbršček, P., Dražić, G., Anžlovar, A., Orel, Z. O. The preparation of zinc silicate/ZnO particles and their use as an efficient UV absorber. Mater. res.

10. Bitenc, M., Dražić, G., Orel, Z. O. Characterization of crystalline zinc oxide in the form of hexagonal bipods. Cryst. growth des. 10: 830-837, 2010.

11. Podbršček, P., Dražić, G., Paramo, J. A., Strzhemechny, Y. M., Maček, J., Orel, Z. O. Growth of zinc oxide particles in the presence of silicon. CrystEngComm. 12: 3071-3079, 2010.

12. Japić, D., Paramo, J. A., Marinšek, M., Strzhemechny, Y. M., Orel, Z. O. Growth-morphology-luminescence correlation in ZnO-containing nanostructures synthesized in different media. J. lumin. 132: 1589-1596, 2012.

13. Baghbanzadeh, M., Škapin, S. D., Orel, Z. C., Kappe, C. O. A critical assessment of the specific role of microwave irradiation in the synthesis of ZnO micro- and nanostructured materials. Chemistry 18 (18): 2724-2731, 2012.

14. Anžlovar, A., Kogej, K., Orel, Z. C., Žigon, M. Polyol mediated nano size zinc oxide and nanocomposites with poly(methyl methacrylate).

Express polym. lett. 5: 604-619, 2011.

15. Anžlovar, A., Orel, Z. C., Kogej, K., Žigon, M. Polyol-mediated synthesis of zinc oxide nanorods and nanocomposites with poly(methyl methacrylate). J. nanomater. vol. 2012, 760872760881, 2012.

16. Anžlovar, A, Orel, Z. C., Žigon, M. Poly(methyl methacrylate) composites prepared by in situ polymerization using organophilic nanoto-submicrometer zinc oxide particles. Eur. Polym.

J. 46: 1216-1224, 2010.

bull. 46: 2105-2111, 2011.

9.

Bitenc, M., Podbršček, P., Dubček, P., Bernstorff, S., Dražić, G., Orel, B., Pejovnik, S., Orel, Z. O. In and ex situ studies of the formation of layered microspherical hydrozinciteas precursor for ZnO. Chemistry 16 (37): 11481-11488, 2010.

49

about CE polimat

Center of Excellence for Polymer Materials and Technologies

CE PoliMaT

T

he Center of Excellence for polymer materials and technologies (CE PoliMaT), based on a public-private partnership, was established on 8 January 2010 by a group of businesses and academic institutions.

In the field of polymer materials and technology, CE PoliMaT ensures the transformation of research excellence into products and services in hightech niche markets, supporting job creation, new business formation, economic development and the transition to a low-carbon society.

CE PoliMaT facilitates research excellence by bringing together leading scientists and engineers from different disciplines, such as chemistry, physics, pharmaceuticals, biotechnology, medicine, and mechanical engineering.

Research focuses on the development of advanced multifunctional materials with the help of nanotechnology and the use of renewable resources. The center develops applications for the use in industry, health, agriculture, building materials, renewable energy and electronics.

50

Through cooperation with leading centers of knowledge in the field of polymers in Europe, United States of America and Africa, CE PoliMaT is leading the way in creating a Global Biopolymer Network.

Contacts

CE PoliMaT, Tehnološki park 24, 1000 Ljubljana, Slovenia, EU T: +386 (0) 59081274 F: +386 (0) 59081279 E: info@polimat.si I: en.polimat.si Innovation office CE PoliMaT Akron Suite 801 F, Akron Global Business Accelerator / AGBA 526 S. Main Street Akron, Ohio 44311 USA

oRGAnIZeRs:

In cLose coLL ABoRAtIon WItH:

sPonsoRs: GoLD

B RonZe

VenUe PRoVIDeD BY

François de Grivel

the operation of PoliMat is partly fi nanced by the european Union through the european Regional Development Fund - budget heading 6944 competitiveness of enterprises and Research excellence - esRR-07-13-eU, accounts 4120 and 4310. 15% of the share of eligible assets represent earmarked funds from the budget of the Republic of slovenia - budget heading 9406 competitiveness of enterprises and Research excellence - esRR-07-13-slovenian participation, accounts 4120 and 4310, nRP-no 3211-09-0012.