Polymerization kinetics of multifunctional monomers and crosslinked structure of the resulting polymers
Abstract
Multifunctional monomers polymerized in bulk form rigid, glassy crosslinked polymers. The kinetic behavior of such diffusion-controlled polymerizations and the structural development of the resulting networks were investigated using poly(ethylene glycol) diacrylates as model compounds. The effects of variations in monomer chain length on the reaction characteristics were analyzed. The coupling of volume relaxations with the reaction kinetics was demonstrated. Dark reaction experiments and thermomechanical analyses pointed to a spatially heterogeneous reaction environment and polymer network. Results from volume shrinkage and swelling studies indicated that the final materials were highly crosslinked. Three mathematical models were developed to describe the polymerization reactions and the network structure. The first used a mean-field approach in which expressions were derived for the calculation of the initiator efficiency, propagation and termination rate constants throughout the polymerization process and these expressions were integrated into the initiation-propagation-termination scheme typical for a free-radical polymerization. Predictions regarding the reaction characteristics were obtained using this model. To be able to simultaneously obtain kinetic and structural information, a second approach was developed. This involved the stochastic simulation of the reaction in which the temporal evolution of all the molecular species in the reaction mixture was followed. Finally, an off-lattice simulation technique was also developed to follow the orientational order of liquid crystalline monomers as a function of temperature and the reaction behavior when such monomers are polymerized. Satisfactory agreement between the results of each model and experimental observations was obtained.
Degree
Ph.D.
Advisors
Peppas, Purdue University.
Subject Area
Chemical engineering
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