Nematic liquid crystals with a trifluoromethyl group

We have synthesised a new class of compounds incorporating a trifluoromethy l group in the terminal alkoxy or alkenyloxy chain. Compounds containing se veral aromatic rings were synthesised with a view to producing compounds of high birefringence. This also included the synthesis of compounds containi ng a carbon-carbon triple bond. Compounds with three 1,4-disubstituted ring s were synthesised in order to produce materials with a high nematic cleari ng point and as low a melting point as possible. Laterally fluoro-substitut ed compounds were prepared to generate a high positive value of the dielect ric anisotropy, a low melting point and no smectic mesophases. Substances c ontaining a cyclohexyl ring, which tend to induce a lower viscosity and com pounds incorporating a bicyclo[2.2.2]octane ring were also synthesised in o rder to produce a high nematic clearing point and to influence the elastic constants. The (E)-trifluorobut-2-enyloxy-compounds were prepared in attemp ts to produce compounds with appropriate elastic constants and a high biref ringence.