Photoisomerization of azobenzenes and spirocompounds in nematic and in twisted nematic liquid crystals

The nematic and twisted nematic liquid crystals mixed with azobenzene (AB), spirooxazine (SO) and spiropyran (SP) are investigated by using spectroscopic methods, including birefringence and polarized transmission, to monitor the amplitude of the changes upon phototransformation as well as the dark kinetics. The results have shown SP to be an interesting photochemical probe as it has orientation photochromism and is able to adequately sense the orientation dependent polarity of this anisotropic medium.