Preparation and performance enhancement of n-eicosane/polyvinyl alcohol/MXene flexible phase change composites with sandwich structure

•Sandwich structure was beneficial for enhancing performance of flexible phase change composites.•Heat storage, mechanical strength and light-to-heat conversion were simultaneously improved.•Outstanding thermal reliability and stability, and temperature regulation ability were demonstrated. In this work, flexible n-eicosane (C20)/polyvinyl alcohol (PVA)/MXene flexible composite PCMs (CPM fc-PCMs) with sandwich structure were designed and prepared. The sandwich structure was prepared by layer-by-layer coating, which was beneficial for enhancing performance of flexible phase change composites. Specifically, the sandwich structure of CPM fc-PCMs could effectively solve the leakage and poor thermal reliability of C20, while significantly improving their thermal storage, mechanical and photothermal conversion performance. The results showed that CPM fc-PCMs had high heat storage capacities, and the maximum latent heat reached ∼157.43 J/g. It was worth noting that the decrease of latent heat of 1CPM70 after 200 phase transition cycles was 2.58 %, showing good thermal reliability due to the micro-morphology and microstructure of CPM fc-PCMs. The addition of MXene with rich surface functional groups could provide hydrogen bonding sites to enhance the bond between layers, so that the CPM fc-PCMs demonstrated excellent flexibility and mechanical performance (∼16.65 MPa). MXene could effectively improve the light-to-heat conversion ability of CPM fc-PCMs, indicating that the CPM fc-PCMs had a good temperature regulation ability in the thermal management of human wearable clothing. In addition, the CPM fc-PCMs demonstrated good thermal stability by TG analysis.