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Thiol-ene Chemistry as an Enabler of New Polymer Structures and Architectures

This dissertation focuses on two distinct projects: the synthesis and design of novel cell penetrating peptides mimics (CPPMs), and the implementation of the thiol-ene click reaction to generate new polymer architectures and chemistries. Guanidinium-rich CPPMs were generated through both ROMP and RAFT polymerizations, allowing for a comparison to be made across polymer backbone chemistries with respect to both siRNA and protein cellular internalization. A particularly effective methacrylate derived block copolymer was able to deliver siRNA to nearly an entire Jurkat T cell population. The thiol-ene reaction was implemented initially within the context of improving material design for solid polymer electrolytes (SPEs), specifically lithium ion separators. Synthesis of styrene-ethylene oxide multiblock copolymer electrolytes by the combination of telechelic di-thiol and di-norbornene polymers was performed. Morphology and conductivity were assessed as a function of conducting block volume fraction, with encouraging results and robust conductivities above a PEO volume fraction of 0.5. Flory-Huggins interaction parameters were also estimated and compared to literature projections. New SPE chemistries utilizing thioethers, sulfoxides, and sulfones were also synthesized through the step-growth polymerization of various di-ene and di-thiol monomers. When doped with lithium ions, these materials demonstrated comparable conductivities to PEO, a benchmark SPE, and could be tuned to eliminate crystallization, a severe drawback of PEO at lower temperatures. These SPEs were also strengthened by polystyrene incorporation, resulting in block copolymer materials that demonstrated a room temperature storage modulus of 0.1 GPa, while maintaining high levels of conductivity. Finally, the universality of the thiol-ene polymerization was demonstrated by the generation of main-chain carbonate, main-chain zwitterion, and side-chain diol polymers. Similarly to the above SPE materials, these polymers contained a thioether functional group that could selectively be oxidized to yield either a sulfoxide or sulfone, without degrading the polymer or affecting the incorporated functional groups. The research described in this dissertation is broad-reaching in the field of polymer science and beyond, covering numerous applications and techniques, and demonstrating improvements upon standard applied materials.
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