This study deals with the preparation and characterization of the composites of polyethylene glycol (PEG)/the synthesized polymeric solid-solid phase change material (SSPCM) as novel form stable phase change material (FSPCM) for thermal energy storage. The synthesized SSPCM can play two roles in the FSPCM: the supporting material and the phase change working substance. The influence of PEG content on crystalline properties and phase change behaviors of the FSPCMs was investigated. The polarizing optical microscopy (POM) images of FSPCMs show that all FSPCMs have the spherocrystal morphology, and the spherocrystal size of SSPCM increases with the increasing of PEG percent. The results from differential scanning calorimetry (DSC) indicate that the prepared FSPCMs with different PEG contents have high thermal storage density, and the enthalpy efficiency of them is much higher than that of the traditional FSPCMs due to the synergistic phase change effect of PEG and SSPCM. The Fourier transform infrared spectroscopy (FTIR) spectrum and DSC curve of the FSPCMs after thermal cycling are almost the same as those of the original samples, which indicates that the FSPCMs have excellent thermal reliability and reusability. The work not only supplied a kind of novel FSPCMs with high performances, but also proposed a new way to solve the problem of enthalpy decline of traditional FSPCMs and synthesized polymeric SSPCMs compared with solid-liquid PCMs. (C) 2014 Elsevier B.V. All rights reserved.