The Synthesis and Properties of Some Novel Ferroelectric Materials-Hosts and Dopants

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Abstract
The first indication that terphenyl derivatives might provide suitable host Sc systems which could be doped with chiral materials and used in ferroelectric smectic C devices arose with 4,4″-dialkyl- and 4,4″-alkoxyalkyl-p-terphenyls carrying a single lateral fluoro-substituent. Subsequently, 4,4″-dialkyl- and 4,4″-alkoxyalkyl-p-terphenyls with 2,3- or 2′,3′-difluoro-substituents (and related biphenyls) have been found to be superior, when doped with appropriate chiral cyanohydrin esters. The synthesis of these difluoro-oligophenyls will be discussed, with particular reference to the use of tetrakis(triphenylphosphine)palladium(0)-catalysed coupling of arylboronic acids with aryl halides. The liquid crystal properties of the various materials will be discussed together with some results relating to the excellent ferroelectric behaviour of the doped systems. These mixtures provide wide range S*c phases, large Ps values, good aligning properties on rubbed polymers, switching times that are fast, and a multiplexing capability consistent with video line address times at room temperature.