wherein each of A is a polymer block of a vinyl arene and B is a polymer block of a conjugated diene; the average molecular weight of A being between about 8,000 and 45,000, the average molecular weight of B being between about 40,000 and 125,000, the total A content of the block copolymer being between about 23 and 40 weight percent; and hydrogenated derivatives of such block copolymers.