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
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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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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
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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[24]; such materials may be readily adapted for biomedical implants. Agricultural resources such as
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engineering [25] and targeted drug delivery [26]. With
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[27]. Agriculture tends to play a significant role in the
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biomaterials: preparation, properties and tissue
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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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initiating hepato carcinogensis in Balb/c mice.
polymer-based scaffolds for bone and vascular
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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
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& Nutrition 2013, in press 15. Neergheen-Bhujun VS, Rosun H, Joonas N,
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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
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Contacts
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oRGAnIZeRs:
In cLose coLL ABoRAtIon WItH:
sPonsoRs: GoLD
B RonZe
VenUe PRoVIDeD BY
François de Grivel
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