Linear polyurethane (PU) ionomers were synthesized as solid-solid phase changing materials (PCMs) for thermal energy storage. Poly(ethylene glycol)s (PEGs) with 6000 and 10,000 g/mol number average molecular weight were used as latent heat storage materials, and 4,4-diphenylmethane diisocyanate (MDI), N-methyldiethanolamine (MDEA) and 1,3-Propanesulfonate (PS) were used as supporting materials. The phase change enthalpies of PU ionomers were 142.5 J/g and 152.3 J/g respectively, which were much close to the highest reported value of the branched PUPCM or the cross-linking PUPCM. The results of Fourier transform infrared spectroscopy (FT-IR) and atomic force microscopy (AFM) suggested a high degree of phase separation existed in PU ionomers. And the thermal resistance of PU ionomers was improved by the introduction of ionic groups. (C) 2014 Elsevier B.V. All rights reserved.