Date of Award

Spring 1-1-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry & Biochemistry

First Advisor

Christopher N. Bowman

Second Advisor

David Walba

Third Advisor

Yifu Ding

Fourth Advisor

Wei Zhang

Fifth Advisor

Charles Musgrave

Abstract

The focus of this research was the application of organic synthesis for new monomer development of Reversible Addition Chain Transfer (RAFT) compounds (i.e. trithiocarbonates and allyl sulphides), and the application of these monomers into photostimuli responsive networks designated as Covalent Adaptable Netowrks (CAN's). A mild, efficient, and high yield synthesis of a variety of trithiocarbonates and allyl sulphide containing AFCT (Addition-Fragmentation Chain-Transfer Termination) monomers containing terminal (meth)acrylate functional groups was presented. The ability of these monomers to control the mechanical and polymerization properties of thiol-Michael and chain-growth polymer networks in a previously unattainable manner is described.

Controllable Reversible Addition-Fragmentation Termination (CRAFT) compounds structure-property relationships related to the RAFT compositional structure as it impacts photoplasticity and in-situ polymerization volumetric shrinkage stress in CAN's was investigated. Synthesizing, evaluating, and systematically varying CRAFT monomers expanded the range and functional capabilities of addition-fragmentation capable network forming monomers. Subsequent assessment of the impact of these monomers on photoplasticity and volumetric stress reduction was performed. With the detailed understanding of the structure-property relationships of the CRAFT monomers, these monomers were employed in networks for new applications in the field of stimuli responsive networks.

The bond reshuffling and bond exchange reactions observed in CAN's were expanded to internetwork reshuffling for the development of on-demand adhesives. The application of polymer networks containing RAFT moieties that promote bond exchange only upon photoinitiation was demonstrated. By incorporation and variation of the RAFT chemical structure a versatile and wide-ranging methodology for adhesion was developed.

Finally, the design of a new RAFT alkyne was employed into thiol-yne networks, and the ability to reduce polymerization induced shrinkage stress in thiol-yne and hybrid thiol-yne systems was demonstrated. A novel mechanism of bond rearrangement by aryl alkynes was discovered. The combination of the yne and AFCT mechanisms permitted the formation of highly crosslinked thermosets exhibiting high refractive indices with minimal volumetric shrinkage stress. In particular, the application of chain transfer motifs into CANs for advances in polymeric materials.

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