Synthesis and Physical Properties of Asymmetric Diphenyldiacetylenic Liquid Crystals

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Abstract
Fifty-six asymmetric diphenyl-diacetylene liquid crystal homologs including dialkyl, alkyl-alkoxy, cyano-alkyl, chloro-alkyl, fluoro-alkyl, difluoro-alkyl, lateral chloro-substituted fluoro-alkyl (or alkoxy), lateral fluoro-substituted asymmetric dialkyl, and vinyl-alkyl are synthesized and their physical properties evaluated. Among these asymmetric diphenyl-diacetylene liquid crystals, many dialkyl homologs exhibit low melting point, wide nematic range, and low heat of fusion. They are ideal host candidates for formulating eutectic mixtures. The polar groups make important contributions to the phase transition temperature, dielectric anisotropy, refractive indices and viscosity. Detailed effects depend on the position of the substitution. These new liquid-crystals compounds and mixtures are particularly useful for electro-optic modulation of infrared radiation.