Living & Learning through Liquid Crystals

BY MAIYA PACLEB

In the first week of March 2020, I submitted my application and proposal for summer research at the university with my mentor Dr. Eric Scharrer. What we didn’t know is that, just about a week later, our world was going to be altered completely. With our world facing the reality of the COVID-19 pandemic, there were doubts about what would constitute our everyday way of living. Soon, us students, along with our professors and faculty, were forced to face the hardships of virtual learning. Little did I know when I applied for summer research that I, as well as billions of people across the world, would have to rely upon the very things that I was studying—liquid crystals.

So, what are liquid crystals (LCs), and why are we dependent on them? Think of your three phases of matter: solid, liquid, and gas. To transition between these phases of matter, you must overcome intermolecular interactions that exist between each molecule to push it into disorder. The amount of disorder ultimately determines the phase of matter. Between solid and liquid phases exists a discrete phase of matter that only some compounds can achieve, and these are classified as LCs. Because of this intermediate state of order LC molecules possess, they are pliable through application of an electric field. Through this malleable property, LC are able to interact with light differently to reflect visual images. The reorientation, or “switching,” of these molecules through electric manipulation and its interaction with light makes up what we know as Liquid Crystal Display (LCD) technology. You probably have seen this widely used in computers, phones, calculators, and televisions. Therefore, LCs makeup how we are able to see anything on the screen, and how we have continued to learn (as best we can) virtually through a pandemic.

ABOVE: Phase transition by temperature, going from solid phase to liquid crystal phase to the isotropic (liquid) phase

However, this LC technology is far from perfect, and research is pushing to reach an optimized display method that would enhance quality and performance. LCD is primarily made up of single major-director containing LC compounds, called the uniaxial nematic (Nu) phase (1). This single major-director can be thought of as an axis that is maintained individually in each LC molecule, and further contributes to a large axis of orientation for a collective group of LC molecules. The nematic phase itself is valuable because there is no specific arrangement of the collective group of LC molecules, so the shape of the LC sample is pliable. Additionally, all of these LC molecules happen to be oriented simultaneously in the same direction. The N u phase inherently provides properties that make it convenient to work with in display applications. Their disadvantage, simply put, is that these N u compounds, both individually and collectively, have a large axis that only directs the compounds in one direction. To achieve reorientation or switching of this single director axis, it takes a lot more time and energy. So, what we really want is to attain a nematic phase that can switch quickly for display applications, taking less energy and providing better visuals. There are more efficient nematic phases of these compounds that can be achieved, namely the biaxial nematic (Nb) phase. The N b phase contains a minor, shorter, perpendicular director that would allow for faster switching. However, these N b exhibiting LC compounds consistently prove to be elusive. The N b phase, first observed in 1,3,4-oxadiazole core LC compounds, was only accessible at temperatures of over 200℃, which is clearly not suitable for use in our everyday devices (3).

ABOVE: Schematic of Nu and Nb phases, with arrows displaying directors of a group LC molecules (2). The blue arrow represents the major director of the LC molecules in both the N u and N b phase. The orange arrow represents the minor, smaller, perpendicular director that is favorable in Nb phases for enhanced display properties.

The purpose of my research was to synthesize and study the phase behavior of three structurally similar nitro-containing 1,3,4-oxadiazole core LCs. The addition of the nitro group (NO2) was important to gaining an understanding of how certain structural elements would alter the interaction of the LC molecules, and possibly allow different phase properties. Then, one element of the structure in each LC derivative, namely the long carbon chains (depicted as R) in the “wings’’ of the compounds, were varied in length. This small structural change would allow our lab to analyze the similarities and differences in the phase behavior that these LC compounds possessed. Ultimately, this structure-behavior analysis would provide more information about the phase properties of LC derivatives, which could provide LC candidates for improved displays. We were specifically searching for a low temperature nematic phase (N b if possible), which would be applicable for excelled displays and broader technological application. Although this project was heavy in organic synthesis that seemed straightforward, it was a tedious procedure. The synthetic timeline requires about a month to synthesize one testable, and pure, oxadiazole compound. Along with chemical synthesis, we utilized methods like nuclear magnetic spectroscopy (NMR), polarizing microscopy, and differential scanning calorimetry to test the integrity of our synthetic efforts. In the end, I created three LC compounds that were stunning and lively under the polarizing microscope.

ABOVE: Structure of nitro-containing 1,3,4-oxadiazole core LC molecule. Distinct sections of the molecule are labelled as oxadiazole core and terminal alkyl “wings.” The nitro, rooting from the core of the compound, is depicted by NO2. The R on the edge of each “wing” is the structural element that was altered for each synthetic procedure, specifically carbon (alkyl) chains, varied from chain lengths of C5 to C7.

After completing my summer of research and continuing to work with Dr. Scharrer into the still virtual school year, I was fortunate enough to receive a nomination for giving an oral presentation for the physical sciences at the 29 th annual Murdock College Science Research (MCSR) Conference. The MCSR Conference encompasses presentations from undergraduate student researchers in various scientific disciplines from private undergraduate institutions within the Pacific Northwest, encompassing Oregon, Washington, Idaho, Montana and Alaska. Though normally this conference would have constituted traveling, with the pandemic persisting into the fall, it was clear that the conference was going to be limited to a virtual format. Not only was I going to be presenting at a regional research conference, but I was going to be doing it through a screen. It was definitely nerve-racking—how do I know if I am making sense if I can’t see anyone’s reactions? How do I engage the audience when I know none of us would love it more than if we could just step away from the screen?

Knowing I already committed myself to the opportunity, there was nothing I could do but practice and hope for the best when my time came. Dr. Scharrer and I met multiple times a week, in the lab and over Zoom, to work through my presentation, understanding, and to practice. When the conference day finally arrived, I was shocked when I was introduced by the pioneer of LC research, Peter Collings (fun aside: his book on liquid crystals was right next to me on my desk when I made the connection). As for the presentation, it was a blur. I know that I was nervous, sweating, and almost got tripped up on some of my words, but finishing felt so relieving. I was also subjected to various questions from conference attendees, ranging from professors to other students, that put my research knowledge on the spot. After listening to the rest of the presentations that day, I didn’t think much about the quality of my presentation or how I answered questions—rather, I felt pleased with having the courage to turn on my camera and microphone to speak. The next day during the awards ceremony, I was completely taken aback when my name appeared on the screen for the MCSR 2020 John Van Zytveld Award in the Physical Sciences. This award was given to the student researcher who was determined by the conference panelist to give the best oral presentation. What the… No way? First off, I (naively) didn’t even know that the conference was judged and gave awards to students (Eric also kept this a secret from me). Second, I did not think that I was even in the top presenters for the physical sciences (as there were so many amazing presenters). It was a complete shock, but I am so thankful for the support that Dr. Scharrer, as well as the MCSR conference cohort showed me during my time at the conference. For it being my first ever research conference, along with the added challenge of it being virtual, it was completely worth the stress, effort, and time.

From my experience as an undergraduate researcher and presenter at the MCSR conference, I learned that it is still possible to achieve what you put your mind to, even when facing unparalleled circumstances. As for now, currently passing a year of virtual learning, we have consistently depended on the research of LCs that make up the human connection that some of us can access today. Although being a virtual student is not perfect by any means, I am thankful that my research has brought me closer to the scientific community and has pushed me to grow as an individual. I am also very aware that my ability to conduct research this past summer during a pandemic put me in a privileged position, and I will never take it for granted. I will forever be grateful for the opportunities that learning about – and though – liquid crystals brought me.

ABOVE: Polarizing microscope image of transition of the C5 derivative from liquid (isotropic) phase to nematic phase. The liquid phase is distinguished by the black, whereas the nematic phase appears colorful

Want to see Maiya’s liquid crystals in motion? Check out our special web content!