Design of flexible polyethylene glycol-based phase change materials by crystal structure regulation

The design of flexible phase change materials (FPCMs) with polyethylene glycol (PEG) as phase change components remains a great challenge due to high crystalline structure makes for high thermal energy storage ability yet deteriorates mechanical toughness. Herein, the preparation strategy of FPCMs was developed by introducing crystal structure regulators (CSRs) in PEG-based FPCM networks in a form of covalent linkages. The hydroquinone CSR had the strongest ability of crystal structure regulation over FPCMs compared to the three other used CSRs. The FPCMs had tuneable phase change temperatures (-2.0 degrees C-49.7 degrees C) and enthalpies (40.7 J g(-1) to 109.3 J g(-1)) depending on the number-average molecular weight (M-n = 4000 Da, 6000 Da) of PEGs used as well as the content and type of CSRs, further enabling tuneable mechanical stress (0.59-15.61 MPa) and strain (5.74%-505.86 %). Compared with the pristine PEGs, the FPCMs yielded excellent shape stability, thermal stability and thermal reliability. The flexibility and phase change properties endowed the FPCMs with excellent self-adaptability and shape memory function. The innovative strategy towards FPCMs highlights the application potential on individual wearable temperature-controlled devices.