Solar-driven bistable thermochromic textiles based on supercooling and space constraint anchoring electron transfer

Abstract

Bistable thermochromic (BTC) materials with distinct and optional color states are promising owing to their energy efficiency and camouflage effect. Herein, solar-driven BTC microcapsules (SDBTC-Ms) are constructed via in situ polymerization, which shows that two separate color states, colored (ST I) and colorless (ST II), coexist steadily and interchangeably in the same environment. A phenyl ester phase change material with suitable supercooling is selected to control the electron transfer channel to lock fluorane in the oxidized (ST I) or neutral (ST II) state. The neutral state is further reinforced by utilizing the space constraint effect of microcapsules, which prevents spontaneous electron transfer by controlling the nucleation rate. Nano-SiC loaded on the shell endows the SDBTC-Ms photothermal conversion properties. Notably, the electron transfer channel ON or OFF state is related to stimulation time and temperature, controlling reversibility and bistability. It memorizes ST II for at least 150 h after stimulating at 60 °C for 3 min but quickly returns to ST I after stimulating for 1 s. Smart textiles (SDBTCT) fabricated using SDBTC-Ms exhibit the same performance. This designed concept provides a feasible scheme for bistable materials.