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A new approach to the synthesis of azulene liquid crystals is described based on Hafner's procedure involving reaction of a pyridinium salt with a cyclopentadienide. The preparation of a variety of liquid crystalline materials using this method is described. Variants are reported with single substituents on the azulene ring in the 6-position and doubly substituted in the 2, 6positions. The effect of the azulene ring as a core or dipolar terminal structural element is explored. 6-(5-Alkyl-1,3-dioxan-2yl )azulenes are shown to exhibit smectic A phases and 2-cyclohexyl-6-(5-tridecyl-1,3-dioxan-2-yl )azulene show smectic A and B phases. Phase characterisation of the materials is recorded together with X-ray measurements on the smectic A phase of one representative compound. Results of dichroism studies on the azulene mesogens are also briefly reviewed.

The first group of fully characterised mesogenic (€,€)-I ,4-diarylbuta-I ,3-dienes, substituted in the para-position of one aryl ring by an alkoxy-group and in the para-position of the other aryl group by a cyano-or halogeno-group has been prepared by a Wadsworth-Emmons procedure; their physical properties of high birefringence and low viscosity i n combination make them particularly suitable for use in liquid crystal display devices when mixed with known liquid crystalline materials.

A group of (€,€)-1.4-diarylbuta-l,3-dienes, substituted in the para-position of one aryl ring by an alkoxy-group and in the para-position of the other aryl group by a cyano-or halogeno-group have been synthesised. The compounds are mesogenic and their physical properties make them suitable for liquid crystal display devices when mixed with known liquid crystal materials.Paper 2/065 1 8E