Date of Award

Fall 2019

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

Chuanbing Tang

Abstract

Commodity polymers are used in every aspect of daily life, and most of these polymeric materials are synthesized using petroleum-derived sources. There are direct environmental consequences to this petroleum dependence including greenhouse gas emissions and climate change. Biomass-based polymers show promise for the mitigation on negative environmental impact, in comparison with petroleum-derived counterparts. However, some biopolymers suffer from low chain entanglement due to bulky or long side chain structures, resulting in poor mechanical properties. In this dissertation work, macromolecular engineering is used to design biomass-derived polymers featuring a variety of structures and functionalities. Additionally, biopolymer properties (including thermomechanical enhancement) and applications such as polymer coatings and stimuli- responsive materials are discussed.

The first part of this dissertation focuses on strategies to overcome poor chain entanglement. Through macromolecular engineering, resultant polymer microstructure can be controlled to produce biomass-based polymers with industrially competitive thermomechanical properties. Specifically, supramolecular interactions are introduced to facilitate chain entanglement of polymers from biomass, which exhibit impressive enhancement of mechanical properties. In Chapter 2,, hydrogen-bonding (H-bonding) is used to enhance interactions between two complementary polymers. One polymer contains pendant acid groups as H-bonding donors that interact with H-bonding acceptor polymers such as poly(4-vinylpyridine). The blending results in well-entangled polymer chains that can dissipate stress and provide enhancement in tensile strength and toughness. While in Chapter 3, metal-ligand coordination is used to promote entanglements within plant oil- derived copolymers. Metal-ligand coordination imparts unique and promising properties on these materials. The stimuli-responsive properties of both materials are also discussed.

The second part of this dissertation focuses on applications of biomass-based polymeric materials. In Chapter 4, focus switches to the development of an industrially relevant free- radical emulsion polymerization approach. A series of copolymers are synthesized featuring a plant oil-derived methacrylate copolymerized with styrene, methyl methacrylate, and butyl acrylate. Finally, a simple oxidative crosslinking strategy is used to enhance mechanical properties and provide strong, tough materials for potential coating applications.

In Chapter 5, epoxy resin nanocomposites are featured for their use as potential shape memory materials. Soybean-oil derived polymers are polymerized onto cellulose nanocrystals (CNCs) using a grafting-from SI-ATRP strategy with subsequent crosslinking using amine-catalyzed anhydride-epoxy curing. The strength of resulting epoxy resins provided an optimal permanent network allowing for good shape recovery, while the tunable glass transition temperature allowed for ease in shape fixity.

Finally, in Chapter 6, the summary and conclusions are given. Additionally, novel strategies for future work in overcoming poor entanglement for other biomass-derived polymers are presented.

Available for download on Wednesday, December 16, 2020

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