Operating temperature control in push-pull azobenzene-doped liquid crystal light-driven devices via a UV absorber

초록

Smart devices such as smart windows and light-shutters that use liquid crystals (LCs) mixed with photo responsive mesogen can be controlled remotely by using light irradiation to exploit the response; in this architecture, complex driving networks are not required. Incorporating azobenzene (azo) into LCs has emerged as a widely adopted strategy for controlling smart windows due to its photoisomerization. However, the nematic-to-isotropic phase-transition temperature T-NI of LC/azobenzene composites is generally far above room temperature (RT, similar to 25 degrees C); this limitation hinders device feasibility at <= RT. To overcome this challenge, we investigated the influence of UV absorbers and push-pull azobenzene on the range of effective operating temperature. We exploit the ability of 2-(4-hydroxyphenylazo)benzoic acid (HABA) to reduce the nematic-to-isotropic phase-transition temperature T-NI of 5CB LC, and of HABA and Tinuvin 477 (R) to convert UV radiation to heat; exploiting these responses yielded smart light-shutters that function at RT.

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