A novel polymeric solid-solid phase change heat storage material (PCM) with polyurethane block copolymer structure (PUPCM) composed of high molecule weight Polyethylene glycol (PEG) as soft segment, 4,4'-diphenylmethane diissyanate (MDI) and 1,4-butanediol (13130) as a chain extender were synthesized by a two step process. DSC, POM, SEM and WAXD tests were performed to investigate the phase transition behaviors and crystalline morphology. The results indicated that the PUPCM showed typical solid-solid phase transition properties, e.g. suitable transition temperature, high transition enthalpy and good thermal stability. It is a functional polyurethane with good energy storage effect, and the heat storage mechanism of PUPCM is the transfer between crystalline and amorphous states of the soft segment PEG of PUPCM, and the hard segment, serving as "physical cross-links", restricted the molecular chain of the soft segment's free movement at high temperature. Thus, PUPCM can keep its solid state in the transition processing. (c) 2006 Elsevier Ltd. All rights reserved.