STABLE LIQUID-CRYSTALS WITH LARGE NEGATIVE DIELECTRIC ANISOTROPY .3.

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 prime -trans-n-pentyl-4-trans-bicyclohexyl) ethane as well as of 1-(4-n-butoxy-2,3-dicyano phenyl)-2-(4 prime -n-pentyl-4-biphenyl) ethane is described. These ethane derivatives as well as 4-butoxy-2,3-dicyano-4 double prime -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 photochemically stable LC mixtures with low viscosity and large negative DELTA epsilon . The mesomorphic properties of some intermediate thiophene and furan derivatives are described.