Stable Liquid Crystals with Large Negative Dielectric Anisotropy - III

The synthesis of 4-n-pentyl and 4-n-butoxy derivatives of 1-(2,3-dicyano phenyl)-2-(4-(4-trans-n-pentyl cyclohexyl)phenyl) ethane and 1-(2,3-dicyano phenyl)-2-(4-trans-n-pentyl-4-trans-bicyclohexyl) ethane as well as of 1-(4-n-butoxy-2,3-dicyano phenyl) -2-(4-n-pentyl-4-biphenyl) ethane is described. These ethane derivatives as well as 4-butoxy-2,3-dicyano-4-n-pentyl p-terphenyl were all high melting and no enantiotropic or monotropic mesophases could be observed. However, they can be used as additives for photochemi-cally stable LC mixtures with low viscosity and large negative Δσ. The mesomorphic properties of some intermediate thiophene and furan derivatives are described.