PHD, Kent State University, 2022, College of Arts and Sciences / Materials Science Graduate Program

Three-dimensional (3-D) tissue scaffolds produce suitable environments for cell growth and proliferation for longer periods of time compared to traditional two-dimensional (2-D) tissue culture and, act as appropriate models for the study of cell-cell/cell-scaffold interactions. 3-D models also allow to study cell activities and their functions as well as to evaluate diseases or tissue damage. Liquid crystal elastomers (LCEs) have intrinsic anisotropy and have shown to promote cell alignment and orientation and the presence of liquid crystals (LCs) at a molecular level with and without the use of external stimuli. The work presented in this thesis is the synthesis, design, and creation of 3-D LCEs scaffolds that support several cell lines to promote tissue regeneration. LCEs scaffolds have shown to meet all tissue scaffold requirements to support cell proliferation and growth since they can potentially be biocompatible, biodegradable and their properties, such as porosity and mechanical properties, can be tuned to adapt and match to different cell lines to obtain a suitable tissue. To tune porosity size and density, a salt leaching method was used. Cellulose nanocrystals (a biocompatible additive) were used as an additive to tune the mechanical properties of LCEs to match the young modulus of specific tissues. Once 3-D LCE scaffolds were produced to specifically match neural-like cell lines, we proceed to co-culture neuroblastoma and a glial cell lines (oligodendrocytes). When neuroblastomas are in presence of oligodendrocytes, myelin sheet is formed around the axon of neurons. We observed myelination of neurons during our co-culturing efforts allowing us to study its formation well over several weeks. Our findings will lead researchers on brain degenerative diseases such as Multiple Sclerosis (MS) to have a more appropriate model to quantify, monitor, and find treatments for demyelination and myelination of neurons. Last but not least, in this thesis we will sho (open full item for complete abstract)

Committee: Elda Hegmann (Advisor); Elda Hegmann (Committee Chair); Robert Clements (Committee Member); Richard Piet (Committee Member); Jennifer McDonough (Committee Member); Edgar Kooijman (Committee Member); Torsten Hegmann (Committee Member) Subjects: Materials Science

Doctor of Philosophy, University of Akron, 2017, Polymer Engineering

Polymer nanocomposites have generated widespread interest towards the development of engineered multifunctional materials and novel hybrid assemblies for high performance applications. The addition of anisotropic nanofillers in a polymer matrix can potentially modify the material's optical, thermal, electrical, or mechanical properties due to the high surface area to volume ratio, with increasing advances and focused efforts toward the development of environmentally friendly, reinforced materials from sustainable resources. In this regard, cellulose nanocrystals (CNCs) are promising nanomaterials derived from the world's most abundant natural polymer. However, one of the key challenges and current barriers towards commercialization is controlling uniform dispersion within the polymer matrix in order to achieve effective reinforcement. The objective of this research aims to gain a fundamental understanding on how to control the dispersion and spatial organization of cellulose nanocrystals in polymer thin films by tailoring the thermodynamic interactions between the host polymer matrix and rod-like nanoparticles. The first part of this dissertation focuses on developing a facile strategy to manipulate the spatial distribution of cellulose nanocrystals in polymer thin films, which are highly susceptible to particle aggregation due to strong hydrogen bonding interactions. A model symmetric diblock copolymer poly(styrene-block-methyl methacrylate) (PS-b-PMMA) was utilized as an ideal nanostructured template to selectively sequester and organize the cellulose nanocrystals via directed self-assembly wherein the CNCs were subjected to a degree of confinement within the multilayered structure. The incorporation of anisotropic nanofillers was observed to perturb the block copolymer (BCP) morphology at relatively low nanofiller concentrations. Surface chemistry modification of the nanoparticle was employed to alter interparticle and particle-polymer interactions and subseq (open full item for complete abstract)

Committee: Alamgir Karim Dr. (Advisor); Younjin Min Dr. (Committee Chair); Sadhan Jana Dr. (Committee Member); Yu Zhu Dr. (Committee Member); Jutta Luettmer-Strathmann Dr. (Committee Member) Subjects: Engineering; Materials Science; Polymers

Doctor of Philosophy, Case Western Reserve University, 2017, Macromolecular Science and Engineering

This dissertation focuses on the design and fabrication of different cellulose nanocrystals (CNCs) polymer nanocomposites, with the goal of impacting the structure-property relationship between CNCs and the CNCs/matrix interactions through the surface functionalization of the CNCs with different chemical functional groups. Chapters 2-4 focus on how CNCs from sea tunicates (t-CNCs) functionalized with different chemical moieties affect the mechanical properties of the resulting nanocomposite. First (Chapter 2), t-CNCs were functionalized with lower critical solution temperature (LCST) responsive poly(oligoethylene glycol)monomethyl ether (meth)acrylates, which were incorporated into a poly(vinyl acetate) (PVAc) matrix to create reversible, thermal stiffening nanocomposites. When placed in water below the LCST the nanocomposites are soft, however, when placed in water above the LCST the nanocomposites stiffened as a result of the collapse of the grafted polymer chains allowing the engagement of t-CNCs nanorods. Secondly (Chapter 3), t-CNCs were used as fillers by functionalizing the surface with carboxylic acid moieties which aided in its dispersion in solvents such as N-methyl-2-pyyrolidone (NMP). The dispersion was further used in the synthesis of polyimide aerogels which demonstrated improved physical and mechanical properties as well as thermal stability with the incorporation of t-CNCs as a filler. Lastly (Chapter 4), by functionalizing the surface of t-CNCs with carboxylic acid and amine moieties, t-CNCs were demonstrated to be electrically active. Applying electric current across aqueous solutions of such t-CNCs, resulted in the fabrication of aligned micron-sized t-CNC fibers. Electrically aligned fiber composites with collagen were fabricated by matching the carboxylic acid/amine ratio of t-CNC and collagen. These aligned nanocomposite fibers demonstrated improved mechanical properties with higher contents of t-CNCs. Chapter 5 highlights the isolation of (open full item for complete abstract)

Committee: Stuart Rowan (Committee Chair); LaShanda Korley (Committee Member); David Schiraldi (Committee Member); Ozan Akkus (Committee Member) Subjects: Chemistry; Materials Science; Polymer Chemistry; Polymers

Master of Sciences, Case Western Reserve University, 2014, EMC - Mechanical Engineering

A modified dual-mode heat-flow meter method and a dynamic plane-source method are used to characterize the thermal conductivity of shape memory polymer composites with tunicate cellulose nanocrystals (CNC) fillers. The CNC fillers are shown to enhance the thermal conductivity of the composites by a factor of three to 0.31 W/m-K in the in-plane direction and by a factor of two to 0.23 W/m-K in the through-plane direction over the neat epoxy. These measurements imply that the thermal conductivity of the CNCs is on the order of 7.3 W/m-K as estimated by a simple composite thermal conductivity model. This investigation is a preliminary step towards future investigation of filler alignment driven thermal conductivity switching properties that may be exhibited by shape memory polymer composites.

Committee: Alexis Abramson (Advisor); Stuart Rowan (Committee Member); Joseph Prahl (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering; Nanoscience; Nanotechnology; Polymers