Gamma ray-induced seeded emulsion polymerization of methyl methacrylate and butyl acrylate was carried out in the presence of polymerizable polysiloxane seed latex, which was obtained by the ring-opening copolymerization of octamethyl cyclotetrasiloxane (D-4) and tetramethyl tetravinyl cyclotetrasiloxane(VD4) catalyzed by dodecylbenzene sulfonic acid (DBSA). After the first seeded polymerization, 3-methacryloxylpropyltrimethoxylsilane (MPS) was added for the second seeded polymerization. The conversion-time curve showed that the first seeded polymerization rate was accelerated much by the polysiloxane seed latex. The final composite lattices also showed good storage stability, mechanical stability, and high electrolyte resistance ability. The morphology of the composite latex particles was found to be a quite uniform fine structure by transmission electron microscopy (TEM). The graft of polyacrylates onto polysiloxane and hydrolysis of MPS were confirmed by Fourier transform infrared (FT-IR) spectroscopy. The mechanical performance, water absorption ratio, surface properties, and transparency of the latex films were also investigated. (c) 2006 Wiley Periodicals, Inc.