C18-Based Phase Change Microcapsules with High Encapsulation Efficiency, High Thermal Conductivity, and Photothermal Conversion Performance

The practical application of phase change materials (PCMs) is limited by the challenge of thermal energy storage density, conductivity, and photothermal conversion efficiency. To address these issues, a series of phase change microcapsules (C18@GO-PMMA) were prepared by in situ free radical polymerization, using stearic acid, n -octadecane (Oct), and n -octadecanol (OD) with 18 carbon atoms as the core material and graphene oxide (GO) combined with poly(methyl methacrylate) (PMMA) as hybrid shell monomer. Thanks to GO’s triple role as Pickering emulsifier, photothermal conversion agent, and thermal conductivity enhancer, the comprehensive performance of microcapsules has been significantly improved. Compared with pure PCMs, the thermal conductivities of SA@GO-PMMA, Oct@GO-PMMA, and OD@GO-PMMA increased by 223.1, 147.8, and 221.1%, respectively, and the photothermal conversion efficiency increased to over 75%. The corresponding microcapsules without leakage demonstrated high latent heat storage capacity, and the encapsulation efficiencies were 92.1, 89.1, and 99.1%, respectively. Moreover, the negligible changes of the thermal storage performance and photothermal conversion efficiency during cyclic testing indicate that the microcapsules have good thermal reliability and cycling durability and have the potential in the field of thermal energy storage. This work provides promising possibilities for improving the performance of the composite PCMs.