Free-radical crosslinking polymerization of unsymmetrical divinyl compounds, 1 Gelation in the polymerization of allyl methacrylate

Abstract

As an extension of our continuing studies concerned with the free-radical crosslinking polymerization of multivinyl compounds, this article deals with the gelation in the polymerization of allyl methacrylate (AMA) as a typical unsymmetrical divinyl compound containing two types of vinyl groups such as methacryloyl and allyl ones having quite different reactivities. Thus, AMA was polymerized in bulk or in a 1,4-dioxane solution using an azo-initiator at 50°C in the presence of lauryl mercaptan as chain transfer agent. The actual gel point was compared with the calculated one according to Gordon's equation by tentatively supposing equal reactivity of both vinyl groups. Tailed molecular-weight distribution curves were observed. The swelling ratios of the resulting gels obtained just beyond the gel point was very high. Thus, the intermolecular crosslinking occurred predominantly in the bulk polymerization. Even in the solution polymerization, the occurrence of intramolecular crosslinking was only a little. This was supported by the r.m.s. radii of gyration and second virial coefficients of resulting prepolymers.