A highly branched polystyrene (HBPS) was synthesized via the cc polymerization of 4-(chloromethyl) styrene with styrene using the self-condensing atom transfer radical polymerization method. The addition of this highly branched polystyrene as a melt modifier for polycarbonate (PC) was attempted. Indeed, the results show that the addition of highly branched polystyrene can decrease the melt viscosity of PC with little chan-e in mechanical properties, although the blends do exhibit lower thermal stability compared with pure PC. Extrapolation shows that all of the blends have an initial weight loss temperature above 450degreesC with a statistic heat-resistant index T-s above 225degreesC. (C) 2004 Wiley Periodicals, Inc.