1-Alkyl-2-(arylazo)imidazoles: Unique Combination of Photochromic and Liquid Crystal properties
Abstract
Photochromism and Liquid Crystals are mainly dominated by the change of structure/orientation upon optical/thermal stimulation. Upon light absorption photochromic molecules show reversible structural change with eligible spectral features. The molecules who transform from the orientational more ordered to less ordered arrangement by thermal/physical stimuli show the properties of LC or mesogen. Photochromic responses in LCs encourage re-alignments upon light irradiation and various other properties of the materials. Photochromism is a disorder phenomenon while LC is an ordered orientation; hence, the design of single molecule with two contradicting properties is challenging. Azobenzenes belong to unique class of photochrome and undergo trans-cis photoisomerization while presence of long aliphatic chains sometime induces the LC properties. In our research, a series of substituted arylazoimidazoles are designed and some of them are susceptible to optical stimulation and a few of the long alkyl substituted 1-Alkyl-2-(arylazo)imidazoles (Raai-CnH2n) show thermally controlled LC behaviour.