Date of Award

5-2024

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

School

Polymer Science and Engineering

Committee Chair

Dr. Sergei Nazarenko

Committee Chair School

Polymer Science and Engineering

Committee Member 2

Dr. Yoan Simon

Committee Member 2 School

Polymer Science and Engineering

Committee Member 3

Dr. Brian Olson

Committee Member 3 School

Polymer Science and Engineering

Committee Member 4

Dr. Derek Patton

Committee Member 4 School

Polymer Science and Engineering

Committee Member 5

Dr. James Rawlins

Committee Member 5 School

Polymer Science and Engineering

Committee Member 6

N/A

Abstract

Structure, thermal, mechanical, gas transport, and free volume properties of thiol-ene based systems are investigated and discussed. In the pursuit of generating low energy-cost polymer membranes for gas separation, it became apparent that UV-curing of thiol-ene materials presented several routes toward achieving this goal. Network structure plays a vital role in determining the gas transport properties of membrane materials. UV photopolymerization techniques provide a means to rapidly vitrify network morphologies which can be tuned depending on choice of monomer. Thiol-ene monomers offer a broad range of precursor materials from which to choose for the design of functional membrane materials.

Chapter I outlines the background and motivation of this dissertation, the basics of UV-cured thiol-ene polymer networks, modification of thiol monomers to tailer thiol-ene material properties, gas transport in membrane materials, and free volume in polymers. The methods used to investigate the phenomena of this work are also described in Chapter I.

Chapter II discusses the effects of silane modifications on thiol-ene polymer free volume and gas transport properties. Our group has shown the ability to modify thiol-ene networks for improved gas permeability while maintaining glass transition temperatures through monofunctional modification of a tetrafunctional thiol. UV-curing allows for the rapid setting or “locking in” of a network with modified precursor components, yielding polymer materials with similar long-range connectivity but slight changes in short-range free volume.

Chapter III again utilizes the ability of UV-curing to “lock in” a thiol-ene morphology for the benefit of improving gas permeability. The approach in this chapter however follows the recent development of hybrid organic inorganic materials known as mixed matrix membranes. Porous inorganic membranes have been shown to exhibit favorable gas transport properties but are limited by high production and operating costs. Here we combine porous zeolites with thiol-enes to fabricate high throughput membranes at low cost.

Chapter IV highlights our discovery of unexpected changes to thiol-ene material properties caused by the presence of solvent during the UV-curing process. We have found that solvent-processed thiol-ene materials, when compared to a chemically identical thiol-ene fabricated without solvent, yield increased glass transition temperatures and lower crosslink densities. The study in this chapter discusses our attempt to explain this phenomenon.

ORCID ID

0000-0003-3682-6392

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