Abstract: The composition disclosed herein involves an oil-extended composition comprising 10-200 parts of oil, preferably 25-125 parts, per 100 parts of a hydrogenated diblock copolymer comprising one block of polybutadiene and one block of a random copolymer of a vinyl arene, such as styrene, and butadiene. This hydrogenated diblock copolymer has improved properties as compared to corresponding hydrogenated random copolymers of the vinyl arene and butadiene, particularly with respect to high temperature properties, oil acceptance and stability against aging.

Abstract: The process disclosed herein involves the preparation of butadiene-styrene copolymers of improved green strength and low running temperature when used in tire compositions, which comprises the steps of polymerizing a mixture of butadiene and styrene in a hydrocarbon solvent having a lithium alkyl initiator therein while the monomer mixture is fed into the polymerization system at a rate slow enough to effect random copolymerization in the resulting polymer backbone, effecting a high degree of branching by conducting the polymerization at a temperature of 90.degree.-175.degree. C. (190.degree.-347.degree. F.) and effecting the final 10-50 percent of the polymerization with a monomer portion containing a higher proportion of styrene than is incorporated into the polymer-backbone, thereby effecting the formation of block polystyrene at the terminals of a plurality of branches. This copolymer of improved green strength and low running temperature is very useful in tire compositions.