Resinous linear copolymers having blocks with a heterogeneity index of 2.3 to 4.5

摘要

A resinous linear block copolymer of a monovinyl substituted aromatic compound and a conjugated diene wherein the polymerized monovinyl substituted aromatic compound blocks have a heterogeneity index within the range of about 2.3 to 4.5. The heterogeneity index is the ratio of weight average to number average molecular weight. Such compositions exhibit high impact strength and can be made either by blending two linear block copolymers made under different conditions so as to give different lengths of the polymerized monovinyl substituted aromatic compound blocks, or by adding the monovinyl substituted aromatic compound and a polymerization initiator in two or more increments prior to adding the conjugated diene.