Cellulose-based phase change membranes with reversible optical transmittance and lignin ester-enhancing photothermal conversion performance

Abstract

Leakage issues and low photothermal conversion efficiencies have limited the application of organic solid–liquid phase-change materials. Herein, cellulose-based phase-change membranes (CPCM-FAS-LUEX) were prepared by physically blending three fatty alcohols (1-dodecanol, 1-tetradecanol, and 1-hexadecanol) with a cross-linked network composed of cellulose 10-undecenoyl ester (CUE), lignin 10-undecenoyl ester (LUE), and octadecyl acrylate (OA) with 2,2′-azobis(2-methylpropionitrile) as an initiator. In addition to being part of the network structure, LUE acted as a photothermal conversion enhancer. During phase change processes, the prepared membranes exhibited reversible optical transmittance, the response temperature of which could be adjusted (21–49 °C) by using different fatty alcohols. Differential scanning calorimetry revealed that the CPCM-FAS-LUEX membranes possessed good thermal energy storage capacities, with melting enthalpies up to 134.9 J/g. The introduction of LUE significantly improved the photothermal conversion performance, with an increase in efficiency from 42.06% to 88.66% at a light intensity of 230 mW/cm2. It is noteworthy that reversible optical transmittance and high photothermal conversion efficiency were achieved in the same materials. Hence, the synthesized CPCM-FAS-LUEX membranes have potential for use in thermal–response materials and solar–thermal storage and conversion systems.