Dry blends of polycarbonate (PC) and a bis-ester tetra-amide were extruded at 305 degrees C with a mini twin screw extruder. The bis-ester tetra-amid e diamide (T6T6T-dimethyl) was composed of two and a half repeat units of Nylon 6, T and had methyl ester endgroups. During the extrusion, a trans-esterification reaction took place between the carbonate groups of PC and the terephthalic ester groups of T6T6T-dimethyl. The concentration of the bis-ester tetra-amide units was varied from 0 to 15 wt%. The PC-T6T6T copolymers were analysed by solution viscometry, infra-red (IR) spectroscopy, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The solvent resistance was determined in chloroform. The trans-esterification reaction in the reaction extrusion process progressed to a large extent. The molecular weights of the reaction extrusion copolymers decreased with increasing bis-ester tetra-amide content due to the trans-reactions. The T6T6T segments in the PC-T6T6T copolymers crystallised during the injection moulding process despite their small segment size and their low contents. Even the crystallinity of the T6T6T units was high. As a result of the presence of this T6T6T crystalline phase, the flow temperature of the copolymers increased as did the modulus at 180 degrees C. Also the solvent resistance was found to improve. (C) 2007 Elsevier Ltd. All rights reserved.