Scalable Thermochromic Composite Based on a Ternary Polymer Blend for Temperature-Adaptive Solar Heat Management.

A scalable and durable thermochromic composite is developed for temperature-adaptive solar heat management using a carbon absorber and a thermoresponsive polymer blend consisting of an isolated polycaprolactone phase (PCL) and a continuous phase of miscible poly(methyl methacrylate) and polyvinylidene fluoride. The ternary blend exhibits reversible haze transition originating from the melting and crystallization of PCL. The refractive index matching between the molten PCL and surrounding miscible blend contributes to high-contrast haze switching in the range of 14-91% across the melting temperature of PCL (ca. 55 °C). The solar-absorption-switching properties of the composite are due to the spontaneous light-scattering switching in the polymer blend and the presence of a small amount of carbon black. Spectral measurements indicate that the solar reflectance of the composite sheet varies by 20% between 20 and 60 °C upon lamination with a Ag mirror. Solar heat management using the thermochromic composite is successfully demonstrated under natural sunlight, thereby realizing a temperature-adaptive thermal management system.