Nematic-to-isotropic photo-induced phase transition in azobenzene-doped low-molar liquid crystals.

The photo-induced phase transition generated by several 4,4'-disubstituted azobenzenes in host nematic low-molar mass liquid crystals was quantified by means of the efficiency, DeltaT(N-I), using polarized optical microscopy (POM) at variable temperature. Non-covalent interactions established between mesogen and azobenzene were the main determinants of the photo-induced phase transition behaviour. The correct design of the chemical structure of the system components allows controlling the temperature range in which the photo-induced mesophase transition occurs. Therefore, more efficient systems were obtained when azobenzenes with an extended aromatic core were used.