Thermophysical properties of interface-engineered graphene oxide/polyethylene glycol composite phase change materials

In recent years, high-conductivity fillers were used to enhance the thermal conductivity of composite phase change materials (CPCMs), yet challenges such as interfacial thermal resistance and poor dispersion remained. In this study, polyethylene glycol was used as the matrix and chemically crosslinked with graphene oxide (GO) to construct a three-dimensional crosslinked network structure. Specifically, graphene oxide was fabricated into a three-dimensional framework and subsequently was loaded with polyethylene glycol, thereby producing a novel functionalized graphene composite phase change material (CPCM). Compared with traditional physical mixing methods, this method significantly increased the thermal conductivity of the composite material by reducing the interfacial thermal resistance, resulting in an almost doubled thermal conductivity. The study systematically conducted structural characterization, thermal property testing, and photothermal performance analysis of the materials. Since this preparation system effectively avoided the introduction of exogenous impurities, it offered a significant advantage in retaining the enthalpy value of the CPCM. The melting enthalpy of physically blended systems reached 157.97 J/g, while cross-linked systems exhibited 173.05 J/g, corresponding to 98.3 % enthalpy efficiency relative to pristine PEG6000 (176.06 J/g), surpassing most reported values in literature. The results of cycling stability and thermal stability experiment also indicated that the crosslinked system possessed outstanding temperature stability and cyclic capability. The retention of enthalpy is still 97.5 % even after 500 cycles. In addition, GO conferred PEG with better photothermal conversion capability, and the highest photothermal conversion efficiency was 85.1 %, which had great application prospects in solar thermal. Furthermore, the leakage resistance test results showed that the composite material had excellent leakage prevention properties. The experiments verified the effective crosslinking mechanism between PEG and GO, indicating that the constructed three-dimensional structure not only optimized the thermal response behavior of the composite material but also enhanced the system's adaptability in multiple thermal environments. These results demonstrate that chemical cross-linking offers clear advantages over physical mixing, providing a promising pathway for advanced low-grade thermal energy storage applications.