Physical Sciences and Mathematics Commons^™

Controlling Degradation With Force And Light, Brad Davis

Dissertations

Stimuli-responsive polymers respond to changes in their environment by altering their physical and chemical properties. Their responsiveness allows them to be used as sensors, mechanical actuators, delivery systems, and can yield either elongated lifetimes through healing mechanisms or shortened lifetimes through triggered degradation. Still a growing field in polymer science, researchers seek to expand the capabilities of these materials by improving their specificity, range, and mechanisms of both the stimuli and the response. The work presented explores stimuli-responsive materials, focusing on mechanical and light stimuli, and how to gain control of the response by specific changes in the polymeric material. …

An Atomistic Study Of The Effects On Mechanical Properties And Bonding Interactions Of Carbon Nanofillers In Nylon 6 Nanocomposites, Michael Roth

Dissertations

Polymers have potential for a wide range of applications. The effectiveness of polymers can be further enhanced through the addition of nanofillers that improve thermal, mechanical, and electrical properties of the polymer. Carbon based nanofillers such as carbon nanotube (CNT), graphene, and carbon nanofibre (CNF) are of particular interest due to their high properties and high aspect ratios. However, limited understanding of the governing interactions of these nanofillers with polymers limits the effectiveness of the final nanocomposite.

The first facet of this dissertation focuses on determining the dominating interactions between pristine CNT and graphene with nylon 6 monomer and the …

Functional Polymers Through Mechanochemistry, Stephen Schrettl, Diedrik W.R. Balkenende, Céline Calvino, Marc Karman, Ana Lavrenova, Laura N. Neumann, Yoshimitsu Sagara, Ester Verde-Sesto, Michela Di Giannantonio, Yoan C. Simon, Katharina M. Fromm, Marco Lattuada, Christoph Weder

Faculty Publications

While coupling mechanical and chemical processes is widespread in living organisms, the idea to harness the mechanically induced dissociation of weak covalent and non-covalent bonds to create artificial materials that respond to mechanical stimulation has only recently gained attention. Here we summarize our activities that mainly revolve around the exploitation of non-covalent interactions in (supramolecular) polymeric materials with the goal to translate mechanical stresses into useful, pre-defined events. Focusing on mechano- chromic polymers that alter their optical absorption or fluorescence properties, several new operating principles, mechanosensitive entities, and materials systems were developed. Such materials are expected to be useful for …

Synthesis Of Acceptors For Use In Donor-Acceptor Copolymers And Characterization Of These Polymers, William D. Walker

Honors Theses

In this thesis, a selenium-derivatized acceptor was synthesized to examine the heavy atom effects of selenium on the position of the frontier molecular orbitals (HOMO/LUMO band gap) as opposed to sulfur in a donor-acceptor copolymer for use in light harvesting and detection applications. Over the course of this research, standard operating protocols for ultraviolet-visible (UV-Vis-NIR) and Fourier transform infrared (FT-IR) spectroscopies, as well as cyclic voltammetry (CV) characterization techniques were established. Once synthesized, the polymers were characterized through use of the established characterization protocols. The selenium-derivatized polymer exhibited a bathochromic shift compared to the sulfur analogue, with a solid-state absorption …

Polymerization Of Blocked Isocyanate Functional Polymer Surfaces And Post-Polymerization Modification By Thiol-Isocyanate Reactions, Chase A. Tretbar

Honors Theses

Direct polymerization of isocyanate-functional monomers has been achieved with controlled radical polymerizations (CRP) for precisely engineered modification platforms with highly reactive side chains. However, despite the success of these strategies, the inherent reactivity of isocyanates still leads to adverse side reactions, such as hydrolysis, that are difficult to suppress. Phenol, lactam, and oxime-based blocking agents have been used to limit the reactivity of isocyanates in applications such as multicomponent urethane coating systems. The reactivity of these blocked isocyanates can be restored by thermal deprotection of the blocking agent to achieve the desired reactions. In this work, we use blocked isocyanate-functional …

Effects Of Varying The Cure Profiles Of An Epoxy-Amine System, Patrick W. Hollingsworth

Honors Theses

The cure of an epoxy prepolymer with an amine hardener induces stress in thermosetting systems. The extent of residual stresses in the cured epoxy-amine thermosets are dependent on several factors; one of which is the cure profile utilized. The effect of cure profile on cure induced stresses of an epoxy-amine thermoset was examined in the current study. A difunctional epoxide based on diglycidyl ether of bisphenol-A (DGEBA) and a tetrafunctional amine curative were used to conduct this study. Two cure profiles were selected to prepare samples of varying degrees of stress in the cured thermosets. The first was constant heating …

Density And Conformation With Relaxed Substrate, Bulk, And Interface In Electrophoretic Deposition Of Polymer Chains, F.W. Bentrem, J. Xie, Ras B. Pandey

Faculty Publications

Characteristics of relaxed density profile and conformation of polymer chains are studied by a Monte Carlo simulation on a discrete lattice in three dimensions using different segmental (kink-jump (K), crank-shaft (C), reptation (R)) dynamics. Three distinct density regimes, substrate, bulk, and interface, are identified. With the KC segmental dynamics, we find that the substrate coverage grows with a power law, d_s∝t^γ with a field (E) dependent non-universal exponent γ=0.23+0.7E. The bulk volume fraction d_b and the substrate polymer density (d_s) increases with the field with power-laws (d_{b …}