<title>High-birefringence dopants for use in ferroelectric and nematic liquid crystal mixtures</title>

Abstract

Ferroelectric smectic C* liquid crystals have been shown to exhibit high speed, electro-optic switching when incorporated into the surface stabilized ferroelectric liquid crystal (SSFLC) light valve. Certain applications utilizing IR modulation, waveguide, and phase modulation, and certain fiber-optic devices, can benefit from materials with a birefringence higher than that typically seen in FLC materials ((Delta) n approximately equals 0.15). A new class of compounds, the tolane cinnamates, was developed to help meet this need. These compounds combine a cinnamate moiety with the well known high birefringence tolane core, resulting in two improvements: first, the birefringence increases from 0.24 to 0.29; and second, the tolane cinnamate system is significantly more stable to UV light than the parent tolane system. The new materials show smectic C as well as nematic phases and demonstrate good compatibility with both nematic and FLC hosts.