A new generation of a series of five-block copolymers of poly( dimethylsiloxane) (PDMS), polycaprolactone (PCL), and polyvinyl pyrrolidinone (PVP), (PVP-PCL-PDMS-PCL-PVP), are synthesized to obtain new polymeric systems containing PDMS with improved compatibilities. For this, a commercial reactive triblock copolymer of PCL and PDMS, namely (PCL-PMDS-PCL), was used as the starting material from which the peroxidic macroinitiator was prepared. By use of physicochemical methods, a five-block copolymer structure was confirmed, and its characterization was accomplished. Mechanical and thermal test results showed higher thermal resistances and increased toughness characteristics of the copolymer as compared with that of the component homopolymers. (C) 1997 John Wiley & Sons, Inc.