Photo-driven change in the polar environment tunes gelation in a nematic liquid crystal

Abstract

We report the effect of photo-isomerisation on physical gelation in a soft nematic organogel. The gel is obtained by the addition of a low molecular weight organogelator and a photo-active azobenzene based compound to a nematic liquid crystal. The UV-induced photo-isomerization is seen to have a substantial influence on the gelation process, as exemplified by dielectric studies. The change in the polar solubility parameter of the gelator environment and its consequence on the gelator–solvent interaction are proposed to be governed by the cis-isomers of azobenzene. This is validated by FTIR, Raman and rheological measurements, demonstrating the importance of solvent polarity influencing the thermal stability and strength of liquid crystal gels.