RESINOUS LINEAR BLOCK COPOLYMER OF A MONOVINYL- SUBSTITUTED AROMATIC COMPOUND AND A CONJUGATED DIENE

摘要

A RESINOUS LINEAR BLOCK COPOLYMER OF A MONOVINYLSUBSTITUTED AROMATIC COMPOUND AND A CONJUGATED DIENE 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 bending two linear block copolymers made under different conditions so as to give different lengths of the polymerized monovinyl-substi-tuted 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. These compositions are particularly useful in applications such as injection molded articles where high impact strength is desirable.