Poly(butyl methylacrylate)-b-poly(dimethylsiloxane)-b-poly(butyl methylacrylate) (PBMA-b-PDMSb-PBMA) triblock copolymers were synthesized by atom transfer radical polymerization (ATRP). The reaction of alpha,omega-dichloride PDMS with 2'-hydroxyethyl-2-bromo-2-methylpropanoate gave suitable macroinitiators for the ATRP of BMA. The latter procedure was carried out at 110degreesC in a phenyl ether solution with CuCl and 4,4'-di (5-nonyl)-2,2'-bipyridine (dNbpy) as the catalyzing system. The polymerization was controllable, with the increase of the monomer conversion, there was a nearly linear increase of molecular weight and a decrease of polydispersity in the process of the polymerization, and the rate of the polymerization was first-order with respect to monomer conversion. The block copolymers were characterized with IR and H-1-NMR and differential scanning calorimetry. The effects of macroinitiator concentration, catalyst concentration, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP were reported. (C) 2004 Wiley Periodicals, Inc.