|Fifth Year Graduate Student|
|Materials Science and Engineering|
|University of Delaware|
Electrostatic polymer processing (electrospinning) is a unique and convenient way to produce both natural and synthetic nonwoven polymer fabrics spanning over several orders of magnitude, from tens of nanometers to tens of microns. Although many fiber production methods have been around for decades, electrospinning is unique not only in the fiber diameter range accessible, but also due to the fact that it can be accomplished at ambient conditions. The applications for electrospinning include tissue engineering, filtration, textiles, composites, and protective clothing, to name just a few. Although the dynamics of the process are still being elucidated, this has not prevented the scientific community from exploiting this interesting phenomenon.
We are currently studying well-defined elastomeric stereoblock polypropylenes that consist of symmetric blocks of isotactic polypropylene covalently attached to a larger block of atactic polypropylene were recently synthesized. While the molecular weights and molecular weight distributions of the samples are comparable, the amount of total isotactic content varies for each polymer. Due to the solubility of these materials in a number of solvents, we were able to electrospin these materials into polymeric fibers. Field emission scanning electron microscopy (FE-SEM) was employed in order to examine the morphology of the resultant fibrous mats as well as the diameters of the fibers. It was observed that as the percent of the isotactic content of the materials increased the morphology of the fibers appeared less fused.
Due to the unique triblock structure of these materials, it is hypothesized that the isotactic portions of each of these materials undergo different crystallization phenomena and thus possess different thermal and structural properties. Fourier transform infrared (FTIR) and Fourier transform Raman (FT-Raman) spectroscopies, as well as differential scanning calorimetry (DSC) have shown that the crystallinity of these materials increases with the isotactic content, and that electrospinning does have a realizable effect on the microstructure of these polymers. We are also currently we are examining these materials with wide angle x-ray scattering (WAXS) in order to discern what effect electrospinning has on the long and short range order, respectively, of these materials.
We have also examined the role of solvent evaporation on the crystalline state of electrospun Nylon 6 fibers by electrospinning into a closed chamber filled with varying concentrations of solvent vapor. It was found that the thermodynamically stable α form became increasingly present in Nylon 6 fibers electrospun out of both 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and formic acid as the vapor phase solvent concentration increased. It is believed that the formation of the metastable γ form is due to the fast solvent evaporation kinetics associated with the electrospinning process. By varying the rate of solvent evaporation during electrospinning, we were able to control the resulting crystal structure of the electrospun Nylon 6, as evidenced by XRD and Raman and FTIR spectroscopies. We are currently examining whether this behavior is universally observed across all families of polymorphic polymers.
Publications & Honors
|“Controlling the Crystalline State of Electrospun Nylon 6 by Varying the Rate of Solvent Evaporation,” C.B. Giller, D.B. Chase, J.F. Rabolt, C.M. Snively (in press, Macromolecules). “Electrospinning and Microstructural Characterization of Architecturally-Discrete Isotactic-Atactic-Isotactic Triblock Stereoblock Polypropylene Thermoplastic Elastomers,” C.B. Giller, G. Gururajan, W. Zhang, J. Wei, L.R. Sita, D.B. Chase, J.F. Rabolt (in preparation). “Molecular Orientation Evolution During Electrospinning of Atactic Polystyrene Using Real-Time Raman Spectroscopy,” G. Gururajan, C.B. Giller, C. Snively, D.B. Chase, J.F. Rabolt (in preparation). “Investigating the Crystallization Behavior of Deuterated Isotactic Segments in Elastomeric Stereoblock Polypropylenes,” C.B. Giller, G. Gururajan, J. Wei, L.R. Sita, D.B. Chase, J.F. Rabolt (in preparation). “Alternate Syntheses of Prodan and Acrylodan,” S.S. Silvonek, C.B. Giller, C.J. Abelt, Organic Preparations and Procedures International, 37, 4, 589-594.|
|Fellowship for International Research, Internships, and Performances for Graduate Students at the University of Delaware: Fall 2009 – used for travel to Grenoble, France to make x-ray measurements on polypropylene elastomers at the European Sychrotron Radiation Facility. NSF Fellowship for Fostering United States-Australian Research Collaborations: Summer 2008 – traveled to Sydney, Australia to establish a research collaboration with Robert Breukers of the University of Wollongong. NSF IGERT Fellowship: Fall 2005 – Winter 2006 I was awarded membership into the Phi Beta Kappa (PBK) academic honor fraternity as an undergraduate. I graduated from the College of William and Mary magna cum laude with a GPA of 3.78 and a member of the Phi Beta Kappa (PBK) academic honor fraternity.|
I attended the College of William and Mary, majoring in chemistry and minoring in mathematics. During my final years at William and Mary, I studied under Prof. Christopher Abelt as a synthetic organic chemist. Although the research was intrinsically interesting, I found my career interests wandering from the pure sciences towards the applied. It was at this point, the summer of 2004, that I decided I wanted to take a more applied route and become an engineer. I applied to the Materials Science and Engineering department at the University of Delaware not only because of the prospect of having an opportunity to see the less abstract and more practical side of science, but also due to the wide variety of research done in this department and the interdisciplinary atmosphere.
I am now a fifth year graduate student in this department. My research specialty is the processing, spectroscopic, and micro- and nanostructural characterization of both commercially availale and specially synthesized polymers. I utilize the fundamental concepts of chemistry that I learned as an undergraduate and apply them in an effort to understand the polymeric systems with which I work. I have had the opportunity to attend close to a dozen conferences during my time here and have helped initiate and maintain collaborations with groups whose different and unique scientific studies and skills has unquestionably added to my general knowledge of materials. I plan on finishing my studies here in about eight to nine months and afterwards going into either the government or industry, using my interdisciplinary experiences, education, and networking skills to accel in whatever scientifiic endeavours I will undertake.