SYNTHESIS AND MESOMORPHIC PROPERTIES OF NEW LIQUID-CRYSTALLINE CYCLOHEXYL-PHENYL-PYRIMIDINES AND DICYCLOHEXYL-PYRIMIDINES

The synthesis and mesomorphic properties of three new classes of cyano-substituted cyclohexyl-phenyl- and dicyclohexyl-pyrimidines are reported. The compounds are colourless, chemically and photochemically stable and have wide nematic mesophases. The thermal compatibility of the new compounds with other nematic liquid crystals is excellent. The large static positive dielectric anisotropics are shown to depend strongly on the position and number of hydrogenated rings as well as on the alkyl chain lengths within a homologous series. The reported bulk viscosities vary considerably among homologues. Hydrogenating the ring adjacent to the cyano end group causes η to increase, whereas a considerable viscosity reduction compared to nonhydrogenated homologues was found by hydrogenating the ring adjacent to the alkyl end group. The measured refractive indices of the new compounds are comparable to those of biphenyls. © 1979, Walter de Gruyter. All rights reserved.