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We have prepared novel preorganized compounds in which 4-(4-fluorophenyl)phenyl and 4-(trifluoromethoxy)phenyl are connected via a rigid catechol unit or a flexible spacer and investigated their structural effects on the induced dielectric anisotropy in the mixture with a host material. The nonsymmetric bimesogenic compounds with the flexible spacer were found to be a dopant with negative dielectric anisotropy in host A composed of fluoro-substituted phenyl esters, whereas they were found to be a dopant with large positive dielectric anisotropy in host B (6OCB). The rigid U-shaped compound enhanced Δε in both hosts A and B. We discuss effects of host−guest interaction on conformational change of the guest molecule in the nematic liquid crystalline phase.

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We prepared novel S-shaped liquid crystal oligomers, the 4,49-bis (v-(2-(v-(4-(cyanophenyl)phenyloxy)alkyloxy)phenyloxy)alkyloxybiphenyls (S-n), and investigated their transition behaviour. The oligomer with even-numbered spacers (S-6) exhibited a nematic phase, whereas the oligomer with odd-numbered spacers (S-7) exhibited nematic and smectic A phases. Transition properties of the S-shaped oligomers are compared with those of the corresponding monomeric and U-shaped dimeric compounds. The entropy changes associated with the I-N transition for the oligomers were found to have small values, similar to that of the monomeric compound. A biaxial smectic phase was induced below the SmA phase in some binary mixtures of S-6 and a phenylpyrimidine derivative (8-PYP-6O). On the other hand, the SmA phase was stabilized in the mixtures of S-7 and 8-PYP-6O. We discuss the transition behaivour of the S-shaped oligomers in terms of their molecular shape.

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.