Abstract: Process for the preparation of an efficient industrial .alpha., .omega.-dilithio poly(conjugated diene) diinitiator having a peak molecular weight in the range of from 1000 to 3000, comprising the reaction of mono-organolithium initiator with diisopropenyl benzene in an apolar hydrocarbon solvent, optionally in the presence of a tertiary amine, followed by addition to the reaction mixture of a small amount of conjugated diene monomer and at least 15 vol % of an aromatic ether activator at a temperature in the range of from 0.degree. to 30.degree. C.; the use of said .alpha., .omega.-dithio initiator for the manufacture of symmetrical block copolymers by anionic polymerization, from monovinylaromatic, conjugated diene and/or polar vinyl compound monomers; and block copolymers so obtained having a combination of a narrow molecular weight distribution (Mw/Mn.ltoreq.1.20) and relatively low vinyl content (.ltoreq.18%).

Abstract: An improved process for the production of linear block copolymers of vinylaromatic hydrocarbon and conjugated alkadiene comprises the coupling of living polymer chains containing at least one block of polymerized vinylaromatic hydrocarbon and at least one block of polymerized conjugated alkadiene wherein the coupling agent is an aromatic phosphonite.