Increasing the reactivity of coupling of block polymers

A process for the preparation of thermoplastic block polymers which comprises contacting conjugated diolefinic monomers selected from the group consisting of isoprene, piperylene, 2-ethyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene and 1,3-butadiene, mixed with at least one polyvinyl aromatic coupling compound selected from the group consisting of o, m and p-divinylbenzene, 1,2,4-trivinylbenzene, 1,8-divinylnaphthalene, 1,2-divinyl-3,4-dimethylbenzene, 2,4-divinylbiphenyl, 3,5,4'-trivinylbiphenyl and 1,3,5-trivinylbenzene under solution polymerization conditions with a polystyryllithium catalyst which has been prepared by reacting an alkyllithium compound with a styrene monomer selected from the group consisting of styrene, alpha-methylstyrene, p-methylstyrene, p-t-butylstyrene, 3-methylstyrene, 1-vinylnaphthalene, in which an amount of polyvinyl aromatic coupling compound ranges from about 1.0 to about 6 vinyl groups of the polyvinyl aromatic coupling compound per mole of active lithium catalyst used, to produce a living polymer and then subsequently contacting said living polymer with (a) a polar compound selected from the group consisting of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 2,3-dimethyoxybutane, N,N,N',N'-tetramethylethylenediamine, tri-n-butylphosphine and hexamethylphosphoric triamide, in which the molar ratio of the said polar compounds to the active lithium, based on the amount of said polystyryllithium catalyst present at the start of the polymerization, ranges from about 0.01/1 to about 20/1 or (B) a polar compound selected from the group consisting of tetrahydrofuran, diethyl ether, triethylamine, 1,4-diazabicyclo-2.2.2-octane, p-dioxane, tri-n-butylamine and N,N'-dimethylpiperazine, in which the molar ratio of the said polar compounds to the active lithium, based on the amount of said polystyryllithium catalyst present at the start of the polymerization, ranges from about 0.5/1 to about 100/1.