Micro mechanism of latent heat enhancement of polyethylene glycol/aminated modified palygorskite composite phase change materials

Surface functional modification of clay minerals showed a positive effect on promoting phase change behavior and improving heat storage characteristic of phase change material (PCM). Currently, there was a lack of quantitative evidence to explain the micro mechanism between surface functional modification and latent heat enhancement. In this work, the dopamine-modified palygorskite/polyethylene glycol (MPP) composite PCMs were prepared and their latent heat enhanced micro mechanism was studied in depth based on density functional theory (DFT) calculations. Due to the strong surface interaction, the phase change behavior of palygorskite/polyethylene glycol composite PCMs was strongly restricted so that no latent heat was released when the content of polyethylene glycol was <50 wt%. After dopamine modification, the latent heat (> 37.63 J/g) of MPP was released when the content of polyethylene glycol was higher than 30 wt%, indicating that the surface interaction was weakened. The DFT calculation results revealed that before and after dopamine modification, the surface interaction changed from weak SiO chemical bonds to no combination approaches and the interaction energy sharply dropped from 195.25 eV to 0.40 eV, demonstrating that the surface interaction between polyethylene glycol and palygorskite was greatly reduced, which was further confirmed by the crystallization and heat storage/release results, which was responsible for the promoted phase change behavior and enhanced latent heat. Furthermore, the MPP exhibited excellent chemical compatibility and acceptable thermal stability. This work was of great significance in revealing the inner relationship between the microstructure and property enhancement of clay minerals-based composite PCMs.