A new class of high birefringence smectic C liquid crystals. 3,3′-Difluorodiphenyldiacetylenes

Abstract

Ferroelectric smectic C∗ liquid crystals have been shown to exhibit high speed, multistate electro-optic switching, particularly when incorporated into the surface stabilized ferroelectric liquid crystal (SSFLC) light valve. Certain applications utilizing IR modulation, waveguide, and fibre-optic devices can benefit from a birefringence higher than the value of Δn = 0·15 seen in typical FLC materials. By incorporating the highly conjugated diacetylene moiety into an FLC core, an increase in birefringence to greater than Δn = 0·3 is achieved. Fluorination of the core induces a strong preference for the tilted smectic C phase as compared to the unfluorinated materials which typically show the nematic phase. The effect of different tail substitutions is examined in the 3,3′-difluorodiphenyldiacetylene system.