Cellulose-derived solid-solid phase change thermal energy storage membrane with switchable optical transparency

A polymerization/crosslinking-induced shape-stabilization strategy was applied to constructed PCM membranes with excellent thermo-reversible optical transparency and remarkable photo-thermal storage performance. • CUE-AAs as novel PCM membranes were prepared via a copolymerization strategy. • Excellent switchable optical transparency and tailored responsive temperature. • High thermal energy storage performance and photo-thermal conversion performance. • Great potential in application as intelligent optical devices. Switchable optical transparency is an intrinsic property for solid–liquid phase change materials (PCMs) during phase change processes. However, due to non-transparent porous confinement materials and core-shell structures, the synthesis of shape-stabled PCMs typically sacrifices their switchable optical transparency. Here, we present a copolymerization-induced shape-stabilization strategy that uses cellulose 10-undecenoyl ester (CUE) as a polymer-based crosslinker and a variety of alkyl acrylates (AAs) as phase change monomers to produce solid–solid phase change membranes (CUE-AAs) with high efficient thermal energy storage and excellent thermo-reversible optical transparency. These as-prepared CUE-AAs membranes present excellent switchable optical transparency from approximately below 5% to over 90% during phase change processes, and the responsive temperature of the transparency could be tailored in the range of 23–67 °C by using different AAs. Furthermore, three kinds of n-alkanes including hexadecane, octadecane, and docosane were physically entrapped in the CUE-AAs cross-linked networks to enhance the thermal energy storage performance, leading to a maximum melting enthalpy of up to 166.5 J/g. Moreover, the introduction of surface modified antimony-doped tin oxide nanoparticles significantly improved the light-to-thermal conversion effect, endowing the resulted membranes with high potential in application as thermal management material. Thus, the diverse properties of these CUE-AAs based PCMs, such as excellent thermo-reversible optical transparency, high thermal energy storage performance, remarkable photo-thermal storage efficiency, and high thermal stability, made them suitable for a wide range of applications, including intelligent optical devices and solar energy storage devices.