Robust phase change materials based on PBAT-block-PEG multiblock copolymers with novel thermostability prepared via facile melt transesterification

Though phase change materials (PCMs) have been demonstrated as a green and sustainable approach to solve the problem of waste heat recovery, preparing PCMs with robust mechanical properties via a simple method remains a massive challenge worldwide. In this study, a facile one-step solvent-free melt transesterification was successfully employed to prepare poly (butylene adipate-co-terephthalate)-block-polyethylene glycol multiblock copolymers (PBAT-block-PEG multiblock copolymers) based solid-solid PCM (SSPCM). The stress-strain curves of SSPCM exhibited more prominent features similar to polymers with high crystallization ability when PEG content was increased, which were furtherly revealed by XRD. The values of tensile strength and elongation at break of most SSPCM, exceeding 3.9 MPa and 669.2 % respectively, represented a significant improvement from previous researches on SSPCM. DSC analysis revealed that PBAT-block-PEG multiblock copolymers based SSPCM containing 60 wt% PEG-6000 (SSPCM-4) exhibited a practical energy storage density with a melting enthalpy of 64.0 J/g. Furthermore, SSPCM-4 not only displayed the solid-solid phase change behavior but also demonstrated impressive mechanical strength by supporting a load exceeding twelve times its weight above the phase change temperature. The solid-solid phase change mechanism was investigated by FT-IR, XRD and H-1 NMR spectroscopy. Moreover, TG analysis indicated that the initial degradation temperature of SSPCM-4 was higher than 200 C-degrees, ensuring its stability during both processing and working.