Copolymerization behaviour of pentadiene-functional macromonomers obtained by free radical addition-fragmentation

Pentadiene-functional macromonomers based on poly (methyl methacrylate) (PMMA) and polystyrene (PS). obtained through a free radical addition-fragmentation reaction were copolymerized with styrene, methyl methacrylate (MMA) and methacrylic acid (MAA) to synthesise well defined graft copolymers. Thus, PMMA-g-PS, PS-g-PMMA and PS-g-PMAA of varying compositions and graft lengths were synthesised. The copolymerization kinetics revealed diminished reactivity of the pentadiene function of the macromonomer towards a given comonomer vis-a-vis the reactivities of the pentadiene monomer or the pentadiene function on the addition-fragmentation agent used to prepare the macromonomers. Methacrylic acid showed apparently reduced reactivity than MMA and the copolymerization of the former with PS-based macromonomer gave amphiphilic graft copolymers with different solubility characteristics. The reactivity of the terminal pentadiene-function of the macromonomer was found to be independent of its molar mass, although its reactivity was marginally diminished in comparison with pentadiene monomer. Low concentrations of high molar mass macromonomer led to the concomitant formation of homopolymers of the small monomer in the case of copolymerization with reactive monomers like MMA and MAA. The graft copolymers have been characterized by chemical methods and by GPC using multiple detectors. (C) 1999 Elsevier Science Ltd. All rights reserved.