Poly(dimethylsiloxane)(PDMS)-based triblock copolymers were successfully synthesized via atom transfer radical polymerization (ATRP) initiated with bis (bromoalkyl)-terminated PDMS macroinitiator (Br-PDMS-Br). First, Br-PDMS-Br was prepared by reaction between the bis(hydroxyalkyl)-terminated PDMS and 2-bromo-2-methylpropionyl bromide. PSt-b-PDMS-b-PSt, PMMA-b-PDMS-b-PMMA and PMA-b-PDMS-b-PMA triblock copolymers were then synthesized via ATRP of styrene (St), methyl methacrylate (MMA) and methyl acrylate (MA), respectively, in the presence of Br-PDMS-Br as a macroinitiator and CuCl/PMDETA as a catalyst system at 80 degrees C. Triblock copolymers were characterized by FTIR, (1)H-NMR and GPC techniques. GPC results showed linear dependence of the number-average molecular weight on the conversion as well as the narrow polydispersity indicies (PDI < 1.57) for the synthesized triblock copolymers which was lower than that of Br-PDMS-Br macroinitiator (PDI = 1.90), indicating the living/controlled characteristic of the reaction. Also, there was a very good agreement between the number-average molecular weight calculated from (1)HNMR spectra and that calculated theoretically. Results showed that resulting copolymers have two glass transition temperatures, indicating that triblock copolymers have microphase separated morphology. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 2423-2430, 2012