Doctor of Philosophy (PhD)
The reaction kinetics and some applications in the field of microfluidics for thiol-acrylate Michael addition polymerizations using multifunctional monomers have been researched and are presented here. The polymerization rate constants for base-catalyzed systems were found to increase with increasing thiol and acrylate functionality, which was attributed to the intramolecular interactions between functional groups. The nucleophile-initiated thiol-acrylate Michael addition polymerization kinetics were monitored via FTIR, and it was determined that the increase in the rate of reaction in these multifunctional systems was significantly less dramatic than the increase observed in monofunctional systems. While no radical polymerization was observed during most typical thiol-acrylate Michael addition reactions, spontaneous radical polymerization can occur in certain systems where the Michael addition rate is low, such as towards the end of nucleophile-initiated reactions, base-catalyzed reactions with low base concentrations, and reactions performed using monomers with low functionality. Several material properties of a thiol-acrylate microfluidic resin (TAMR) were investigated including the cure kinetics, hydrophilicity, solvent absorption, and elastic modulus. The material was shown to cure at 50 °C in 3 hours or at room temperature in 10 hours. The water contact angle of these materials was shown to vary based on the hydrophilicity of the resin curing surface, but it is generally lower than other microfluidic materials, such as poly(dimethylsiloxane) (PDMS). The swelling of TAMR in a variety of solvents was quantified and determined to be superior to PDMS in organic solvents. The elastic modulus of TAMR was shown to vary with cure time and resin formulation with a maximum of ~10.5 MPa for the systems studied. A simple surface modification of ix the TAMR was performed using a thiol-acrylate Michael addition reaction between thiol groups on the resin surface and a modifying acrylate. Two microfluidic applications of TAMR have been presented. The first is a fluorescence-based bacterial detection device which uses the selective binding of bacteria to an antibody bound to the TAMR surface to confirm the presence of the pathogen. The second device uses a thiol-acrylate hydrogel in combination with TAMR to produce a gradient-generating microfluidic device for studying algal chemotaxis.
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Tullier, Michael Perrin, "Thiol-Acrylate Polymerization Kinetics and Applications in Microfluidics" (2016). LSU Doctoral Dissertations. 4209.