Synthesis of solid–solid phase change material for thermal energy storage by crosslinking of polyethylene glycol with poly (glycidyl methacrylate)

Polyethylene glycol (PEG10000)/poly (glycidyl methacrylate) (PGMA) crosslinked copolymer as a novel solid–solid phase change material (SSPCM) was successfully synthesized through the ring-opening crosslinking reaction of end-carboxyl groups in carboxyl polyethylene glycol (CPEG) and epoxy groups in PGMA. Fourier transform infrared spectroscopy (FT-IR), polarizing optical microscopy (POM), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and thermogravimetry (TG) were employed to study the chemical structure, crystalline properties, phase transition behaviors and the thermal stability of the copolymer, respectively. The results from WAXD patterns and POM images show that the crystalline form of the copolymer is similar with that of pure PEG, and the PEG soft segment phase transition between crystalline and amorphous states results in heat storage and release of the copolymer. Due to the crosslinking network restricted the free movement of the soft segments, at temperature above the PEG phase melting transition, the copolymer was still solid. The DSC results indicate that the copolymer imparts balanced and reversible phase change behaviors at the temperature range of 25–60 °C, and it has high latent heat storage capacity of more than 70 J/g. The TG results suggest that the copolymer had a much broader applicable temperature range compared with pure PEG.