Polystyrene-b-poly(dimethylsiloxane)-b-polystyrene (Pst-b-PDMS-b-PSt) triblock copolymers were synthesized by atom transfer radical polymerization (ATRP). Commercially available difunctional PDMS containing vinylsilyl terminal species was reacted with hydrogen bromide, resulting in the PDMS macroinitiators for the ATRP of styrene (St). The latter procedure was carried out at 130degreesC in a phenyl ether solution with CuCl and 4,4'-di (5-nonyl)-2,2'-bipyridine (dNbpy) as the catalyzing system. By using this technique, triblock copolymers consisting of a PDMS center block and polystyrene terminal blocks were synthesized. The polymerization was controllable; ATRP of St from those macroinitiators showed linear increases in M-n with conversion. The block copolymers were characterized with IR and H-1-NMR. The effects of molecular weight of macroinitiators, macroinitiator concentration, catalyst concentration, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP are reported. (C) 2004 Wiley Periodicals, Inc.