A temperature-responsive polyurethane film with reversible visible light transmittance change and constant low UV light transmittance

We prepared a temperature-responsive polyurethane (PU) film with reversible visible light transmittance change, which was opaque at room temperature and became transparent when the temperature rised. The PU film has very low visible light transmittance of 1.4% at room temperature. At 45 °C, the PU film has relatively high transmittance of 66.7% looking translucent. When the temperature goes to 50 °C or above, the transmittance is more than 80% and the PU film is transparent. The reason for this interesting phenomenon about visible light transmittance change was illustrated by polarizing optical microscope and differential scanning calorimetry. While ultraviolet light transmittance of the PU film is very low at all time. Moreover, this PU film has excellent mechanical performance in a wide temperature range. We suppose this PU film has potential applications in many fields such as tunable optical devices or coating materials with smart temperature responsivity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47140.