Date of Award

Spring 2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

School

Polymer Science and Engineering

Committee Chair

Sergei I. Nazarenko

Committee Chair School

Polymer Science and Engineering

Committee Member 2

Robson F. Storey

Committee Member 2 School

Polymer Science and Engineering

Committee Member 3

Jeffery S. Wiggins

Committee Member 3 School

Polymer Science and Engineering

Committee Member 4

Yoan C. Simon

Committee Member 4 School

Polymer Science and Engineering

Committee Member 5

Ras B. Pandey

Committee Member 5 School

Mathematics and Natural Sciences

Abstract

Although a lot of research was conducted on dendritic polymers, our understanding of their structure-property is still limited. Our previous study, which focused on a family of dendritic polymers based on 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) as a monomer, discovered unique hydrogen bond organizations contributed by their dendritic structures. However, the influence of the H-bond organization on bulk properties has yet to be understood. The goal of this dissertation is to elucidate the correlation between the H-bond organization with the dielectric and volumetric properties of bis-MPA based dendritic polymers, with an emphasis on developing a fundamental understanding of to what extent structural irregularity affects the bulk properties of dendritic polymers.

Chapter I of the dissertation provided a background of dendritic polymers with special focus on those based on bis-MPA, the formation of hydrogen bonding, H-bonded clusters, and the H-bond mediated mesophase in bis-MPA based dendritic polymers, and a brief introduction of dielectric spectroscopy. In Chapter II, the chemical nature, the formation of hydrogen bonding, volumetric, and thermodynamic properties of a bis-MPA based dendrimer and hyperbranched polymer (HPB) were carefully analyzed and compared. In chapter III, the gamma-relaxation of both the dendrimer and HBP was investigated via dielectric spectroscopy, where unique dielectric properties, such as high dielectric constant, were observed, especially for the dendrimer. Via molecular dynamics simulation, unique dielectric properties were ascribed to the formation of the H-bonded clusters. In chapter IV, combined with dynamic mechanic analysis, the relaxation of both the dendrimer and HBP detected at high temperatures by dielectric spectroscopy was ascribed to the proton hopping through hydrogen bonds via the Grotthuss mechanism. The influences on H-bonded clusters on the proton hopping process were also analyzed. In Chapter V, the study of the correlation between hydrogen bonding formation and bulk properties was extended to a linear copolymer system based on dimethanol-functionalized norbornene. It was discovered that the formation of hydrogen bonding, which is affected by the stereochemistry of the monomer, plays an important role in defining the gas barrier property of the copolymers.

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