Graft copolymerization with styrene and methyl methacrylate in very viscous medium

The influence of the viscosity of the medium on the rate and efficiency of a chemically initiated graft copolymerization with styrene and methylmethacrylate was studied. The increase in viscosity was reached partly by formation of the respective homopolymers, partly by the atactic polypropylene. The transfer constant to the atactic polypropylene from growing polystyrene macroradicals and the ratio of the rate constants of reaction of primary radicals with atactic polypropylene and with styrene were determined. It was found that the total efficiency of grafting styrene to atactic polypropylene increases with increasing concentration of polypropylene in the initial mixture and that the conversion of monomer is not a major influence in this case. On the contrary, for grafting of methyl methacrylate to atactic polypropylene a decrease of total efficiency with conversion of monomer was observed. This indicates that the gel effect is not only a function of viscosity of medium but also of the character of polymers in the reaction mixture.