Two types of silicone oil, poly(dimethyldiphenyl siloxane) (PDMDPS) and poly(dimethyl siloxane) (PDMS), were added to polycarbonate (PC), and the morphological, mechanical, rheological, and thermal changes of the PC/silicone oil were investigated. A scanning electron microscope showed that the dispersed droplets of the silicone oils in the PC matrix and the size of the dispersed phases were enlarged with increasing amounts of silicone oil. A transition from brittle to ductile failure was observed with increasing PDMDPS. The impact strength of neat PC at -30 degrees C was 8 kg(f) cm/cm, which increased to 52 kg(f) cm/cm with the addition of PDMDPS. It appears that, at low temperature, the phenyl group in PDMDPS is more effective for toughening. A higher decomposition temperature and the bulkier molecular structure of PDMDPS, compared to PDMS, resulted in a smaller increase in the melt flow index of PC/PDMDPS than for PC/PDMS. The glass transition temperature, initiation temperature of thermal weight loss, and heat distortion temperature of PC/silicone oil systems were decreased with an increase in the silicone oil. The blending of PC with PDMDPS provided a practical way to develop a combination of high tensile strength and impact strength at a low temperature with applicable comprehensive properties. (c) 2008 Wiley Periodicals, Inc.