GRAFT-COPOLYMERIZATION OF STYRENE ONTO ETHYLENE-VINYL PARA-NITROBENZOATE COPOLYMER BY CHAIN TRANSFER-REACTION

The effect of steric hindrance on the attack of growing polymer radicals to the reaction sites on a trunk polymer was examined in the graft copolymerization of styrene onto a trunk polymer with pendant aromatic nitro groups by chain transfer reaction of growing polymer radicals to the pendant nitro groups. The nitro groups on ethylene-vinyl p-nitro benzoate copolymer (EVNB) are more effectively utilized in the graft copolymerization than those on the vinyl p-nitro benzoate homopolymer (PVNB) previously used as a trunk polymer, because the nitro groups are distributed less frequently on the trunk polymer in the former than in the latter. This was also confirmed by the higher chain transfer constant of growing polystyrene radicals to EVNB compared to that of PVNB.