Light induced shifts of ferroelectric mesophase transitions

Several series of recently synthesized chiral azobenzene liquid crystals ex hibit transitions driven by both illumination and temperature: some compoun ds can be 'melted' from the SmC* phase to the isotropic phase by increasing illumination only; according to the phase sequences, SmA, TGBA, N*, and bl ue phases are also involved in such behaviour. The observed phenomena are r eversible and transition temperatures are reproducible in identical light c onditions. Some specific transitions have been studied. Their temperatures can be lowered to 10 degrees below the dark transition values by increasing the illumination of samples. Under illumination, those transitions exhibit first order behaviour.