REACTION-KINETICS AND VOLUME RELAXATION DURING POLYMERIZATIONS OF MULTIETHYLENE GLYCOL DIMETHACRYLATES

A series of multiethylene glycol dimethacrylates (MEGDMA) was characterized with respect to the polymerization behavior, kinetics, and mechanisms. By studying a series of MEGDMA's with the number of ethylene glycol units ranging from 2 to 14, the influence of the monomer structure, especially with respect to the system mobility, was determined. For each monomer, the propagation and termination kinetic constants were quantified as a function of conversion to provide insight surrounding the controlling polymerization mechanisms. In particular, the importance of reaction diffusion as a termination mechanism was elucidated. When termination was reaction diffusion controlled, the proportionality constant between the termination kinetic constant and the propagation kinetic constant was found to be the same for all of the MEGDMA's studied and had a value between 2 and 3. The influence of the double bond concentration on the reaction diffusion mechanism was also investigated by polymerizing diethylene glycol dimethacrylate in the presence of an inert solvent. Finally, in addition to characterizing the general reaction behavior, the influence of volume relaxation on the polymerization behavior and kinetics was studied. It was found that in polymerizations of PEG600DMA volume relaxation did not influence the kinetics and the system free volume was nearly independent of rate. However, in DEGDMA, volume relaxation was found to be significant beyond 10% conversion and led to an excess free volume during polymerization performed at higher rates.