In the present study, polyethylene glycol (PEG) were blended with acrylic polymers like polymethyl methacrylate (PMMA), Eudragit S (Eud S), and Eudragit E (Eud E) as novel form stable phase change materials (PCMs) and characterized by optical microscopy, spectroscopy and viscosity techniques. Latent heat thermal energy storage (LHTES) properties of the blends were evaluated by using the differential scanning calorimetry (DSC) technique. In the form-stable blends, PEG acted like phase change-LHTES material when the acrylic polymers served as supporting material because of their adhesion property. The maximum percentage of PEG was found 80% w/w for any of the blend in which no leakage of PEG occurred for 100 heating/cooling cycles. The optical microscopy investigations revealed that the phase behavior of the blends was observed as self organized PEG distributed in the matrix of acrylic polymers rather than chain-like structures. The interactions between the blend components (PEG and one of the acrylic polymers) were analyzed by Fourier transform inftared (FT-IR) spectroscopy and the viscosimetry technique. The key LHTES properties (melting and fteezing temperatures, and latent heats of melting and freezing of the blends) were evaluated by DSC The DSC results indicated that PEG/PMMA, PEG/Eud S, and PEG/Eud E blends as form-stable PCMs were convenient materials for LHTES applications in terms of their satisfying thermal properties. Therefore, these form-stable PCMs could be incorporated into an LHTES system with the advantage of direct utility in order to store daytime solar energy for space heating. (c) 2006 American Institute of Chemical Engineers.