Four beta-cyclodextrin/4,4'-diphenylmethane diisocyanate/polyethylene glycol (beta-CD/MDI/PEG) crosslinking copolymers with different crosslinking density were prepared and characterized as novel polymeric solid-solid phase change materials (SSPCMs) for thermal energy storage. In the SSPCMs, PEG acts as the phase change functional chain and beta-cyclodextrin (beta-CD) acts as the molecular framework. The results from wide-angle X-ray diffraction (WAXD) and polarizing optical microscopy (POM) show that the synthesized SSPCMs have good crystallization properties and spherocrystal morphology with smaller size than that of PEG. According to the results of differential scanning calorimetry (DSC) and thermo-gravimetry (TG) curves, the SSPCMs possess high phase change enthalpies, good reusability, thermal reliability and stability. It is concluded that the crosslinking density of SSPCMs is a crucial factor significantly influenced the free movement and crystallization of PEG segments, and then affects phase transition properties of SSPCMs. (C) 2015 Elsevier B.V. All rights reserved.