A difunctional initiator was synthesized through the addition reaction of tert-butyllithium (t-BuLi) to 1,3-diisopropenylbenzene (DIB) in the presence of triethylamine (Et3N). Under optimized conditions, that is dropwise addition of a mixture of DIB and Et3N to a stirred toluene solution of t-BuLi at 50 degreesC at a molar ratio of DIB/Et3N/t-BuLi = 1/2/2, the difunctional initiator was formed without oligomeriazation of DIB. Copolymerization of butyl acrylate (n-BuA) and methyl methacrylate (MMA) with the difunctional initiator in the presence of bis(2,6-di-tert-butylphenoxy)ethylaluminum [EtAl(ODBP)(2)] in toluene at low temperature proceeded in a monomer-selective manner; n-BuA is polymerized first, followed by MMA polymerization, to form an ABA-type triblock copolymer [PMMA-block-poly(n-BuA)-block-PMMA], which exhibits microphase separation. (C) 2003 Published by Elsevier Ltd.