Initiator Reactivities in Graft Copolymerization

Abstract

The reactivities of initiator were studied from the dependence of graft efficiencies on the type of initiator. Graft copolymerization was performed at 60, 70, and 80°C in the cases of four systems: Polymethylmethacrylate-, poly (p-chlorostyrene)-, polystyrene- and poly (ethyl a-chloroacrylate)-2-methyl-5-vinylpyridine. In each case the homopolymers were separated from the graft copolymers by extraction. The different initiators used were benzoyl peroxide (BPO), lauroyl peroxide (LPO) and azobisisobutyronitrile (AIBN).
Graft efficiencies were varied with the different initiators and decreased slightly with increasing temperature of polymerization. The order of efficiencies was in order of LPO>BPO>AIBN. The differences in efficiencies could be explained by the primary radical attack to the trunk polymers, which depends on the nature of the initiator.
It was concluded that the primary radicals of LPO are less stabilized in resonance than that of AIBN.