We would like to report here novel molecular design for electro-optic liquid crystal devices, i.e. catechol derivatives for reduction in threshold voltage and binaphthyl derivatives for blue phases with a wide temperature range. A threshold voltage of a nematic mixture consisting of a host liquid crystal and 10wt% of a catechol derivative, 1-{6-(3,4-difluorophenyloxy)hexyloxy}-2-{6-[4-(4-fluorophenyl)phenyloxy]hexyloxy}benzene, was markedly lower than that of the host LC. The U-shaped compound was found to induce larger dielectric anisotropy in the nematic phase of the mixture than the corresponding monomeric compound. Then, we prepared a homologous series of novel chiral dimeric compounds, (R)-2,2'-bis{6-[4-(2-(2-fluoro-4-butyloxyphenyl)pyrimidine-5-yl)phenyloxy]alkyloxy}-1,1'-binaphthyl. The binaphthyl derivatives with an even number of atoms in the spacers showed a chiral nematic phase, however, those with an odd number of atoms showed a blue phase in a relatively wide temperature range between the isotropic and smectic A phases. We discuss structure-property relationships in the U-shaped system.
Novel non-symmetric dimeric liquid crystal, 1-(4-cyanobiphenyl-4'-yloxy)-11-[2-(4-octylphenyl)pyrimidine-5-yloxy]undecane (8YP11OCB), has been prepared and the physical properties investigated by means of optical microscopy, differential scanning calorimetry (DSC), X-ray diffraction and dielectric measurements. The crystal structure has been determined to understand microscopic behavior of the compound. Electro-optical properties for 8YP11OCB were compared to those for 1-(4-cyanobiphenyl-4'-yloxy)-11-[4-(5-octylpyrimidine-2-yl)phenyl-4"-oxy]undecane (8PY11OCB). 8YP11OCB with smaller dielectric anisotropy than 8PY11OCB was found to show a lower threshold voltage in the smectic A phase than 8PY11OCB. Crystal structure of 8YP11OCB indicates that three types of core-core interactions exist and that the enthalpy gained by the specific interactions stabilizes the molecular packing with large free volume in the SmA phase.
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