PRODUCTION OF SUSTAINABLE THERMOPLASTICS AND THERMOPLASTIC ELASTOMERS THROUGH CONTROLLED CATIONIC POLYMERIZATIONS
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The design, development, and implementation of sustainable polymers is paramount to the preservation of our planet. Three grand challenges lie before us in this aim: a) generating monomers from renewable resources or waste feedstock, b) the synthesis of robust polymers with material properties comparable to current plastics, and c) the design of end-of-life solutions. The development of economically viable biorenewable plastics is often hindered by the production and availability of chemical feedstocks as well as the efficiency of monomer synthesis. We have identified bioalcohols as an underutilized resource, where they can be efficiently transformed into vinyl ether monomers. Recent advancements in controlled cationic polymerizations have enabled the polymerization of vinyl ethers into sustainable polymers. Specifically, we have demonstrated the synthesis of ABA block copolymers using cationic reversible addition-fragmentation chain-transfer (RAFT) polymerization. The cationic RAFT method used is performed at room temperature, marking an improvement over previous methods for cationic polymerization that relied on low temperatures to maintain a controlled process. The polymers produced were entirely composed of sustainable vinyl ethers and performed comparably to commercial thermoplastic elastomers. Further improvement of this system led to the discovery of a new, “green” chain transfer agent (CTA) for cationic RAFT polymerizations. We then demonstrated the utility of this CTA in chemical, electrochemical, photochemical, and acid-initiated cationic RAFT polymerizations, where it performed better or comparably to previous CTAs. Another notable development in cationic polymerizations has been the advent of a single-component acid initiator that allows for controlled cationic polymerizations under ambient conditions. We employed this acid initiator in the polymerization of the biorenewable cyclic vinyl ether 2,3-dihydrofuran (DHF). Under inert conditions, we were able to achieve high molecular weights (up to 256 kg/mol) and these samples revealed strong and tough tensile properties. Leveraging PDHF’s susceptibility to oxidative degradation, we developed an accelerated degradation method for reducing PDHF to oligomers over 48 hours. This comprehensive study of PDHF revealed this thermoplastic to be strong, tough, sustainable, and degradable. Combined, the advancements in cationic polymerization methods outlined in this work explicate the opportunity available in producing polyvinyl ethers from bioalcohols to provide robust, sustainable, and degradable plastics to meet the grand challenges of today.
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201 pages
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2022-08
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Elastomers; Polymers; Sustainable; Thermoplastics
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Fors, Brett P.
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Coates, Geoffrey
Lin, Song
Lin, Song
Degree Discipline
Chemistry and Chemical Biology
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Ph. D., Chemistry and Chemical Biology
Degree Level
Doctor of Philosophy
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Government Document
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Attribution 4.0 International
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dissertation or thesis