Gel formation in frontal polymerization of 2-hydroxyethyl methacrylate

Frontal polymerization of 2-hydroxyethyl methacrylate was investigated to study the effect of type and concentration of initiator, solvent and diluent on the existence of a front, on front velocity as well as front temperature. A significant effect of the type of initiator and its concentration was recorded. Poly(2-hydroxyethyl methacrylate) (PHEMA) was obtained predominantly as a gel. The different gels were evaluated for water and cyclohexane gain and porosity, and the mechanism of gel formation is discussed. Amongst the three diluents used (silica gel, beta-cyclodextrin and silica sol), gel formation was highest in the presence of silica sol (approximate to42%). Pore dimensions were less than 15 nm and pore size distribution was narrow. PHEMA networks showed significantly higher water regain due to swelling than attributed to the pore volume as estimated by mercury porosimetry or cyclohexane regain. Kinetics of the equilibrium swelling ratio was studied.