Abstract
Bulk polymerization of diallyl phthalate (DAP) was conducted radically at 80 t and the process of growth of resulting gel with the progress of polymerization beyond gel point was investigated in detail. The gel fraction in the polymer obtained beyond gel point increased rapidly with conversion, and thus the polymerization system changed toward the copolymerization of gel with unreacted monomer. For example, the gel fraction in the polymer obtained at 50% of conversion was more than 90%, that is, the resulting gel was swollen by approximately equal amount of monomer. Thus, the polymerization proceeded heterogeneously in a swollen gel at a late stage of polymerization, but no abnormality of polymerization behavior was observed compared to that at an early stage of polymerization. These results may suggest the microheterogeneity of polymerization system; the microheterogenization of the resulting gel, i. e., microgelation, would proceed rapidly beyond the gel point and at a late stage of polymerization the unreacted monomer mainly polymerize at microspaces among microgels. These are supported by the drastic decrease of swelling ratio of resulting gel with the progress of polymerization beyond gel point, the conversion dependence of residual unsaturation and reduced viscosity of gel, and the permeability of solvent into gelled polymerization system.
