Model copolymers of poly(butadiene) (PB) and poly(dimethylsiloxane) (PDMS), PB-b-PDMS-b-PB, were synthesized by sequential anionic polymerization (high vacuum techniques) of 1,3-butadiene and hexamethylciclotrisiloxane (D-3) on sec-BuLi followed by chlorosilane-coupling chemistry. The synthesized copolymers were characterized by nuclear magnetic resonance (H-1 NMR), size-exclusion chromatography (SEC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). SEC and H-1 NMR results showed low polydispersity indexes (M-w/M-n) and variable siloxane compositions, whereas DSC and TGA experiments indicated that the thermal stability of the triblock copolymers depends on the PDMS composition. (c) 2007 Wiley Periodicals, Inc.