Tolane cinnamates—a new class of stable, high birefringence dopants

Abstract

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 (Δ≊ 0.15). A new class of compounds, the tolane cinnamates, was developed to help meet this need. They were made by attaching a cinnamate moiety to the well known high birefringence tolane core. This resulted in two improvements: first, the birefringence increased from 0.23 to over 0.3; and second, the tolane cinnamate system was significantly more stable to UV light than the parent tolane system. The new materials showed smectic C as well as nematic phases and demonstrated good compatibility with both nematic and FLC hosts.