Date of Degree

2-2019

Document Type

Dissertation

Degree Name

Ph.D.

Program

Physics

Advisor

Steve G. Greenbaum

Committee Members

Ryann C. Hoffmann

Hyungsik Lim

Yuhang Ren

Sophia N. Suarez

Subject Categories

Biological and Chemical Physics

Keywords

Polyimide, Free Radicals, Material Chemistry, Electron Paramagnetic Resonance, Nuclear Magnetic Resonance

Abstract

Studies of free radicals in the physics, chemistry, biology, and materials science have contributed to advancements in those fields. The presence of radicals can damage the material and system in some instances and, in some cases, they may enhance the property of the material as well. Knowledge of free radical transformations helps in resilience of certain polymers and inhibition of the oxidation of food and medicine. In this thesis, using the magnetic resonance techniques, EPR and NMR, the generation of free radicals and their effect on the structure of the material is being studied.

Kapton Polyimide (PI, Kapton®) used in space missions as a thermal management blanketing material makes it vulnerable to the ionic, proton and electronic radiations when exposed to outer space environment. Modification of PI’s chemical structure occurs and therefore have a dramatic impact on the electronic conductive behavior. The recovery mechanism (free radical evolution) of PI in vacuum and air after having been subjected to 90 KeV electron irradiation is studied in this research.

Melanin, a biopolymer formed by polymerization of quinone radicals, is intriguing study among scientists because of their unique structural and optoelectronic properties. To tune this polymer for various applications melanin -like tripeptides are synthesized and properties of those peptides based on free radical polymerization are studied. Finally, enhancement in conductivity of PEDOT: PSS electrodes used in opto-electronic devices is being studied by probing the behavior of the charge carriers, especially polarons under the effect of magnetophoresis.

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