Polymeric infrared reflective thin films with ultra-broad bandwidth

A polymeric liquid crystalline film was fabricated by photo-induced diffusion and mesogenic phase structural transition of photopolymerisable acrylate monomer mixtures that presented phase transition between cholesteric (Ch) and smectic (SmA) phases. By controlling the curing temperature to be close to SmA–Ch phase transition, a novel architecture that combined Ch and SmA-like short-range ordering (SSO) nanostructures was obtained, which reflected light with the wavelength from 0.5 to 11.5 µm. Experimental results showed that the existence of UV-absorbing dye and curing temperature were critical for the creation of asymmetrical super wide pitch gradient distribution. Moreover, the reflection wavelength and bandwidth of the cholesteric liquid crystal (CLC) films were tuneable by adjusting proportion of the compounds, and the bandwidth could be broadened up to 13 μm. It was expected to have great potential applications in fields like architectural energy conservation or infrared-stealth.