Graft polymers with preset molecular configurations

It has previously been shown that, when a graft polymer of rubber and polymethyl methacrylate is dissolved in benzene and a limited amount of methanol added, the hydrocarbon rubber chains collapse to form colloid particles stabilized by the still soluble polymethyl methacrylate chains. Similar high solids dispersions of this type and of the complementary type with the vinyl polymer chains collapsed have now been prepared and evaporated down to give dry modified rubbers. Due to the known incompatibility between different polymers the microseparation in the colloid suspension is carried through to the dry polymer. It is shown that the form with rubber chains collapsed, polymethyl methacrylate chains extended, is hard, shows modulus reinforcement, and adheres strongly to glass, while the form with polymethyl methacrylate chains collapsed, rubber chains extended, is soft, shows no modulus reinforcement, and does not adhere to glass. This indicates that the extended chains mainly govern these particular properties. On the other hand, good hot tear strength seems to be conferred by the collapsed rubber chains, the alternative form with extended rubber chains giving poor tear at all temperatures. The possibility of predicting the configuration and hence the mechanical properties given by any particular method of preparation is discussed and examples are given.