Poly(styrene-co-maleic anhydride)(SMA)-graft-polyethylene glycol)(PEG) copolymers were synthesized as novel polymeric solid-solid phase change materials (S-SPCMs). The synthesized copolymers showed latent heat storage and release ability by means of the phase transition from crystalline phase to amorphous phase of PEG bonded to the skeleton as side chains. The chemical structures of the polymeric S-SPCMs were confirmed by fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (H-1 NMR) analysis techniques. The transformation of crystalline phase to amorphous phase were investigated using and polarized optical microscopy (POM) techniques. The latent heat thermal energy storage (LHTES) of the S-SPCMs were measured by differential scanning calorimetry (DSC) analysis method. Thermal degradation temperature limits of the S-SPCMs were determined by thermogravimetry analysis (TGA) method. The DSC analysis indicated that the synthesized S-SPCMs demonstrated typical solid-solid phase transitions in the temperature range of about 40-45 degrees C and had considerable high latent heat capacity between 107 and 155 J g(-1). The TGA results showed that the polymeric S-SPCMs were durable thermally up to at least 300 degrees C. The thermal cycling test exposed that the S-SPCMs protected their LHTES properties even after 5000 heating/cooling treatment. All findings indicated that the prepared SMA-graft-PEG copolymers posses good thermal energy storage (TES) potential for passive solar heating and cooling applications.