Poly(butyl acrylate-g-styrene) graft copolymers were prepared by free-radical polymerization using a polystyrene macromonomer carrying a methacryloyloxy group at the chain end and they were characterized by size-exclusion chromatography, and Fourier transform infrared spectroscopy. Glass transition temperatures and deg radation behavior were determined by thermal analysis. Only a single glass transition temperature was observed for the resulting graft copolymers, indicating the miscibility between the poly(styrene) phase and poly(butyl acrylate) (pBA) phase in the graft. copolymer. The incorporation of polystyrene segments in the graft copolymer improved the thermal stability of pBA and enhanced the apparent activation energy for the thermal degradation of pBA.