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Ferroelectricity is desirable for realizing fast-response liquid crystal devices. Existing ferroelectric liquid crystals are improper with the spontaneous polarization Ps being indirectly induced by the broken centrosymmetry of molecular arrangement. We found that Langmuir monolayers of certain dialkylated nematic compound exhibit a laterally polarized two-dimensional ferroelectric nematic. The Ps is comparable to that of chiral smectic liquid crystals, and shows a fast linear electro-optic switching with a microsecond response. Estimates of electrostatic energy suggest that the ferroelectricity may be driven by the direct dipolar interactions.

Zigzag defects in surface-stabilized ferroelectric liquid crystals (SSFLCs) originate from the structural transformation from C1 to C2 chevrons during the cooling process. This transformation occurs so as to accommodate the increasing cone angle of the FLC under the constraint of the surface anchoring. Based on this scenario of defect formation, we propose a new scheme to obtain zigzag defect-free SSFLCs in which the C1–C2 transformation is suppressed by the use of an interfacial layer that has a gradually decreasing SmA–SmC* transition temperature toward the substrate.

We studied the dielectric behavior in the ferroelectric SmC* and ferrielectric SmCγ * phases of the antiferroelectric liquid crystal (R)-1-methylheptyl-4-( 4′′-n-dodecyloxybiphenyl- 4′ carbonoyloxy)-3-fluoro-benzoate. In the SmCγ * phase, 3 dielectric relaxations were recognized in the frequency range under consideration. The 2 relaxation processes at low frequency with high dielectric loss were attributed to azimuthal fluctuation of the molecules around the cone angle ϕ. Those relaxations are investigated as functions of temperature and applied bias electric field. Besides the 2 low-frequency loss processes, one additional loss process with weak intensity was observed.

The dielectric behavior of the antiferroelectric liquid crystal (R)-1-methyl- heptyl-4-( 4′′-n-dodecyloxybiphenyl- 4′ carbonoyloxy)-3-fluorobenzoate was investigated by dielectric spectroscopy. In the antiferroelectric SmC A * phase three dielectric active processes were detected. At least one of them, the process at high frequencies, can also be observed in the ferrielectric phase. In addition to this absorption at high frequency, two other processes with weak intensities around 1 kHz and 50 kHz were detected. These processes are described as functions of temperature, bias voltage and oscillating voltage.

We have investigated molecular motion and ordering in the smectic phases of a nonoriented antiferroelectric liquid crystal by means of C-13 NMR and powder X-ray diffraction. The marked line broadenings for core carbons observed by C-13 NMR indicate the existence of the characteristic molecular motion for the molecular core in the antiferroelectric chiral smectic C (SmC* A) phase. In the smectic phases appearing during the cooling and heating processes, local and overall molecular motions of each molecule observed by C-13 NMR are discussed in comparison with long-range order inside the layer observed by X-ray diffraction.

We have designed a new chiral part, the 2-fluoro-2-methyl alkanoyloxy group and prepared new ferroelectric liquid crystals having this chiral part. The magnitude of spontaneous polarization of 4-(2-fluoro-2-methylhexanoyloxy)phenyl-4'-octyloxybiphenyl-4-carboxylate is about 7 times larger than that of a non fluorinated analogous compound. This remarkable increase of the P s value should be attributable to a fluorine attached together with a methyl group directly to the chiral carbon. Moreover, the effect of the core structure on the spontaneous polarization is also discussed. Introduction of a pyrimidine ring in the core part greatly enhances the spontaneous polarization, over 400 nC/cm2.

In order to clarify the role of intermolecular interaction, effects of alkyl chain length on the rotational viscosity are investigated in two types of FLC mixtures: a totally chiral compound system and a chiral-compound-doped system. Only in the case of the chiral-compound-doped system does a long alkyl chain, which can produce the strong intermolecular interaction, provide the low rotational viscosity. In this system, ferroelectrically triggered orientation change of a small amount of chiral molecules induces the orientation change of a large amount of non-chiral molecules. It is suggested that the strong intermolecular interaction between the chiral and non-chiral molecules is required in order to amplify the molecular orientation change efficiently.

We report the preparation of new ferroelectric liquid crystals, 4-(2-methylalkanoyl)phenyl 4'-alkyloxybiphenyl-4-carboxylates, and the measurements of their physical properties. The dependence of the magnitude of the spontaneous polarization on the alkyl chain length is observed. 4-(2-Methyloctanoyl)phenyl 4'-octyloxybiphenyl-4-carboxylate shows extremely large spontaneous polarization, 293 nC/cm2 (at 62°C) and 403 nC/cm2 (at 39°C).

Novel antiferroelectric chiral smectic C (SmCA *) materials are presented. Four homologous compounds having a 2-alkyl alkanoyl group in the chiral part are investigated. Three of them have SmCA * and show very short helical pitch in SmC*. In contrast, the other one has no SmCA * and exhibits rather long pitch in SmC*. This result suggests that the length of the pitch relates closely to occurrence of SmCA *. The introduction of an ethyl group into the chiral carbon instead of a methyl group increases the stability of SmCA * in contrast with decreasing that of SmA and SmC*. All four compounds show the third state even in SmC* by application of an AC field. Microscope observation indicates that the third state in SmC* is different from that in SmCA *.

In binary mixtures consisting of a non-chiral Sc material and chiral dopants having a 2-methyl alkanoyl chiral part, the effect of alkyl chain length of the chiral dopant on rotational viscosity is investigated. FLC mixtures containing the chiral dopants with a long normal aliphatic chain exhibit low rotational viscosity, which is considered to be provided by the strong lateral intermolecular interaction. This consideration is supported by the fact that mixtures having a stable smectic phase, which is usually attributable to the strong lateral intermolecular interaction, show low rotational viscosity.