Broadband reflective liquid crystal films induced by facile temperature-dependent coexistence of chiral nematic and TGB phase

A wide pitch gradient covering the near infrared region (750.0-2500.0nm) were facilely obtained by simple controlling temperature difference to LC mixtures with a twist grain boundary (TGB)-N* phase transition. After the pitch gradient formed, the structure of broad reflective bandwidth was fixed through polymerisation of monomers in mixtures by UV irradiation. It was found that the temperature difference between the up and down side of the samples was critical to form wide-pitch gradient distribution. Additionally, the reflection wavelength and bandwidth of films could be adjusted by the applied temperature difference with the widest bandwidth up to 1750nm. This simple method for the preparation of broad reflective films was expected to be used in the fields like architectural energy conservation or infrared shield. [GRAPHICS]