Doctor of Philosophy, Miami University, 2019, Chemistry and Biochemistry

Using dynamic chemistry to develop functional polymers is an emerging area in material science. This class of polymers possesses intrinsic reversibility owing to the covalent or noncovalent bonds within, therefore respond to external stimuli. In addition, combining dynamic interactions with polymers offers exciting dynamic features such as environmental adaptivity, malleability, self-healing, and shape memorizing properties. Noncovalent interactions, e.g., hydrogen bonds, metal-ligand coordination, host-guest interactions, ionomers or π-stacking, have been successfully built into polymers over the last decades. Researchers have also relied on dynamic covalent bonds, e.g., Diels-Alder adducts, disulfide exchange, imine bonds, or boronic ester bonds. However, the underlying kinetics of some covalent interactions have not been demonstrated explicitly. Besides, the dynamic nature of the crosslinkers introduces the potential for the material not only the weak toughness but also to creep or deform over time under load. Recently, a combination of dynamic and static crosslinkers on either the main polymer chains or side chains with different structures has been used to overcome these limitations and enhance the mechanical properties. Other than that, materials containing orthogonal dynamic chemistries enable the synthesis of intricate macromolecules which can respond to multiple stimuli to achieve the desired response. Our work mainly focuses on a deep understanding of the mechanism of the covalent interactions in terms of small molecule models to better manipulate them in the bulk polymers, making new dynamic materials, and exploring the impact of the macromolecular architectures on their properties. A mechanistic study of the thermally activated dynamic covalent chemistry of thiol-Michael adducts is the focus of Chapter two, using a model system of thiophenol/mercaptoethanol dynamic equilibrium with phenylvinylketone based Michael acceptors. Chapter three works on f (open full item for complete abstract)

Committee: Dominik Konkolewicz (Advisor); Scott Hartley (Committee Chair); Richard Taylor (Committee Member); Gary Lorigan (Committee Member); Jessica Sparks (Committee Member) Subjects: Chemistry; Materials Science; Organic Chemistry; Physical Chemistry; Polymer Chemistry; Polymers

Master of Science, Miami University, 2015, Chemical, Paper and Biomedical Engineering

This thesis reports the development, and subsequent 3D printing, of a two-part polyacrylamide-alginate interpenetrating network (IPN) hydrogel material with tissue-mimetic properties. Two possible applications include medical simulation and tissue engineering. Material development was performed with single-parameter chemical concentration variations from a baseline formula to establish mechanical property trends. The concentrations of total monomer material and acrylamide crosslinker have the largest effect on elastic modulus and stress relaxation behavior, respectively. Results demonstrate that these hydrogels can be tuned to closely mimic both the elastic and viscoelastic behaviors of muscle tissue. Hardware alterations to a 3D printer allowed the two-part solution to be rapidly printed with high shape fidelity and similar mechanical properties to native tissue at a relatively low cost and on a large scale. The alginate-polyacrylamide material can be tuned in its bulk state, and 3D printed into constructs that are in the correct scale for use in tissue-mimetic applications.

Committee: Jessica Sparks PhD (Advisor); Jason Berberich PhD (Committee Member); Justin Saul PhD (Committee Member) Subjects: Biomedical Engineering; Chemical Engineering

Master of Science, University of Akron, 2006, Chemistry

The synthesis of the phosphazene trimers, [P(OPh)2N]3 and [P(OCH2CF3)2N]3 were performed successfully. Also, the polyphosphazenes, [PCl2N]n, [P(OPh)2N]n and [P(OCH2CF3)2N]n, were synthesized successfully. The syntheses of the trimeric phosphazenes were investigated first to learn the chemistry and behavior of the polymers. Improvements to trimeric yields were reported, due to procedure modifications. Polymeric macromolecular substitution was sucessfully formed on [P(OPh)2N]n when starting with a cross-linked [PCl2N]n. The synthesis of an Interpenetrating Polymer Network (IPN) involving polypropylene and [PCl2N]n was inconclusive. The data suggest an apparent IPN appears to have been formed; whereas, the [PCl2N]3 is acting as a plasticizer for polypropylene.

Committee: Claire Tessier (Advisor) Subjects: