Phototunability, reversible, reflective coloration

Diarylethene Dopants In the reversible phototuning of reflection color in CLCs using azobenzenes or overcrowded alkenes, all the photoresponsive dopants experienced photoisomerization but were accompanied by competing thermal back relaxation. For example, azobenzenes can transform from the trans form to the cis form... 

Tamaoki et al. reported a series of planar chiral dopant which was employed in commercially available nematic LC to achieve phototunable reflection colors [69, 70]. These compounds were designed based on an azobenzenophane compound having conformational restriction on the free rotation of naphthalene moiety to impose an element of planar chirality. Due to the good solubility, moderately high HTPs, and large changes in HTPs during photoisomerization of the dopant, a fast photon mode reversible color control in induced CLCs was achieved. 

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