Synthesis, Characterization and Evaluation of Photo/ Thermal Base Generators for Thiol-Michael Addition Polymerization Reactions

Zhang, Xinpeng

Graduate Thesis Or Dissertation

Synthesis, Characterization and Evaluation of Photo/ Thermal Base Generators for Thiol-Michael Addition Polymerization Reactions Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/sq87bt737

Abstract

The focus of this thesis is to develop effective methodologies to achieve spatiotemporal control over the thiol-Michael addition reaction and to enhance the fundamental understanding of this reaction as well as to broaden its applicable range. With the attributes of quantitative reaction yield, rapid reaction rate, and the ability to be conducted at mild reaction conditions, thiol-Michael click reaction acts as a powerful tool for material synthesis, bio-conjugation and polymer functionalization. Firstly, the control of the thiol-Michael addition polymerization was achieved by the development of two visible light sensitive photobase generators, namely Coumarin-TMG and MNPPOC-TMG. By measuring the photolytic efficiency, catalytic efficiency towards the thiol-Michael addition reaction, the photobases were demonstrated as suitable photoinitiators for the visible light initiated thiol-Michael polymerization. The MNPPOC-TMG catalyzed thiol-Michael polymerization can readily reach over 90% conversion in 5-10 minutes at appropriate visible light conditions. Furthermore, the photobase initiated thiol-Michael addition polymerization was combined with radical initiated acrylate homopolymerization to form a wavelength-selective dual stage polymer network. The thiol-Michael polymerization and the acrylate polymerization were sequentially initiated with lights at different wavelengths, enabling the material to be dual photopatternable at two distinct polymerization stages. The potential applications of this dual stage material were demonstrated in nanoimprint lithography (NIL) and shape memory polymer (SMP). Thirdly, TEMPO catalyzed thiol-Michael addition polymerization was evaluated. A strong base is generated through the thiol-TEMPO oxidation-reduction reaction and this temperature-dependent reaction enables TEMPO to be used as a potential thermal base generator for thermally initiated thiol-Michael addition reaction. As a whole, this dissertation mainly aims at developing suitable initiators for the light/ heat induced thiol-Michael addition polymerization reaction and explore its use in practical applications.

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