Reversible photochemical phase transition behavior of alkoxy-cyano-substituted diphenylbutadiene liquid crystals

Reversible photochemical phase transition behavior of some alkoxy-cyano-substituted diphenylbutadiene liquid crystals has been studied. The EE isomers of these derivatives were found to undergo photoisomerization to yield thermally stable EZ and ZE isomers, which could be transformed back to the EE isomer using light of a different wavelength. On photolysis, the liquid-crystalline EE isomers of these derivatives exhibited isothermal phase transition to the isotropic phase due to the formation of the non-liquid-crystalline EZ and ZE isomers. The thermal stability of the EZ and ZE isomers ensures that reverse switching of these materials to the liquid-crystalline phase remains purely a photon-controlled process.