Influence of the initiator on the grafting of polyvinyl polymers

Abstract

Abstract The dependence of grafting on the type of initiator has been examined in the case of three polymer–monomer systems: polystyrene–methyl methacrylate, polymethyl methacrylate–vinyl acetate, and polyethyl α‐chloroacrylate–vinyl acetate. The different initiators used in these experiments were benzoyl peroxide (Bz 2 O 2 ), azobisisobutyronitrile (AIBN), di‐ tert ‐butyl peroxide (DTBP), and tert ‐butyl hydroperoxide (TBHP). In each case the graft copolymers were separated from the homopolymers by fractional precipitation or by extraction. In the case of the system polystyrene–methyl methacrylate, an appreciable degree of grafting as well as formation of graft copolymer occur in the presence of Bz 2 O 2 ; in contrast, the grafting is low with DTBP and doubtful with AIBN. For the other two systems no noticeable differences occurred as function of the initiator. In the case of polyethyl α‐chloroacrylate the amount of graft copolymer is exceptionally high owing to the sensitivity of this polymer to a radical attack; this sensitivity results in the partial insolubility of the graft copolymers in the presence of TBHP and DTBP, but not in the presence of AIBN.