In this article, a novel solid-solid phase change heat storage material was synthesized via a two-step condensation reaction of high molecular weight poly (ethylene glycol) (PEG4000) with poly(vinyl alcohol) (PVA) and 4,4'-diphenylmethane diisocyanate (MDI). To characterize the resulting product in comparison with pristine PEG4000, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analyses, and polarization optical microscopy measurements were employed to investigate functionality, thermal properties, and crystalline behavior. The results indicated that the crosslinking phase change material showed typical solid-solid phase transition properties, and its phase change enthalpy reached 72.8 kJ/kg. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2041-2045, 2009