Synthesis and properties of some novel high birefringence phenylacetylene liquid crystal materials with lateral substituents

Abstract

We have synthesized and investigated new 3-ring phenylacetylene liquid crystals with high birefringence values (Δn) to improve the nematic temperature range while retaining a high optical anisotropy. In the case of modifying the terminal ring, the introduction of branched alkoxy chains, fluorine or methyl groups shifted the nematic phase to lower temperatures. In order to minimize the influence of the substituent on Δn, the incorporation of lateral methyl groups was chosen as the most profitable method for obtaining wide and low temperature nematic phases. With these results in mind, we studied the effect of the position of the methyl group on the physical properties. The most effective methyl position for improving the nematic temperature range was on the central ring. From the standpoint of obtaining high Δn values and low viscosity, the central ring was also the best position.