Patent ID: 7504454

Claim:
A process for the preparation of a functionalized, coupled or starred block copolymer which is usable in a sulphur-cross-linkable rubber composition comprising carbon black and of reduced hysteresis in the cross-linked state, one at least of said blocks consisting of a polyisoprene and at least one other block consisting of a diene elastomer other than a polyisoprene the molar ratio of units originating from one or more conjugated dienes of which is greater than 15%, wherein said process comprises: (i) copolymerization of one or more monomers comprising at least one conjugated diene other than isoprene using a catalytic system comprising a hydrocarbon solvent, a compound A of a metal of group IIIA, a compound B of an alkaline-earth metal and a polymer initiator C comprising a C—Li bond which is formed of a monolithiated non-functionalized polyisoprene intended to form said polyisoprene block, and (ii) addition to the product of said copolymerization of a functionalizing, coupling or starring agent comprising an acetoxy group of the formula R n —Sn—(O—CO—R′) 4−n , where n is a natural integer of from 0 to 4 and where R and R′ are each alkyl, cycloalkyl, aryl or aralkyl groups which are identical or different, so that said block formed of a diene elastomer other than a polyisoprene is functionalized, coupled or starred.