NETWORK FORMATION IN THE FREE-RADICAL COPOLYMERIZATION OF A BISMALEIMIDE AND STYRENE

Network formation during copolymerization of styrene with a model bism aleimide, p-maleimidobenzoic anhydride, or with mixtures of p-maleimid obenzoic anhydride and methyl p-maleimidobenzoate was studied. The con centrations of pendent double bonds in copolymers, calculated from the consumption of monomers and copolymer composition, follow the general trend typical for vinyl-divinyl copolymerizations. A substantial frac tion of pendent maleimide bonds remains in the system at the end of po lymerization. The gel point conversions are much higher than for ring- free copolymerizations due to cyclization and steric hindrance of pend ent double bonds. The gel point conversions increase with increasing c ontent of the monomaleimide in the copolymerization mixture reaching 1 00% at 4 mol% of bismaleimide (12 wt% solution). The gel point convers ions also increase with increasing dilution reaching 100% for the bism aleimide polymerization in 3 wt% solution. The steric hindrance effect on pendent double bond reactivity seems to be somewhat higher than fo r conventional vinyl-divinyl copolymerizations. Copyright (C) 1996 Pub lished by Elsevier Science Ltd.