Influence of the chemical structure of multifunctional acrylates and methacrylates on their UV photopolymerization kinetics, the crosslinked structure of the ensuing polymers, and their physicochemical properties
Abstract
Highly crosslinked networks were produced from multifunctional monomers by free radical photopolymerization reactions. The multifunctional monomers exhibited limiting conversions, autoacceleration and deceleration in highly exothermic reactions and produced heterogeneous, glassy polymers. The monomers used progressively differ in monomer pendant group, number of pendant double bonds, and rank. The monomer differences allow the observation of reaction and mechanical property differences due to the different functional groups on the monomer. Multifunctional monomers were selected to study the fundamental importance of the functionality, or number of double bonds, the rank or distance between double bonds on the monomer molecule, and the pendant group on the kinetics and final properties of the ensuing polymer. The ultimate goal of this work was to tailor the polymer properties by the selection of the appropriate multifunctional monomer. The kinetics of the photopolymerizations were studied using differential photocalorimetry and attenuated total reflectance-Fourier transform infrared spectroscopy. The photopolymerization reactions were combined with a monomer extraction technique to determine the unreacted monomer concentration. Delayed volume shrinkage was determined from the combination of the dilatometric technique and differential photocalorimetry. A real-time attenuated total reflectance-Fourier transform infrared spectroscopy technique was developed to spatially resolve the photopolymerization reaction. Thermal analysis techniques were used to determine the mechanical stability, strength and glass transition temperature of the multifunctional (meth)acrylate polymers. Thermal analysis was used to determine the relaxation behavior following the polymerization reaction. The experimental studies were designed to estimate a molecular weight between crosslinks. Rubber elasticity theory, swelling theories and theoretical reaction methods were used to calculate crosslinked structure parameters to compare polymer networks from the various monomers studied.
Degree
Ph.D.
Advisors
Peppas, Purdue University.
Subject Area
Chemical engineering
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