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The recently discovered 'banana' B2 mesophase was exhibited on a liquid crystal consisting of bent-core molecules doped with photoactive azobenzene.

A new study investigates the time-resolved dielectric and photoabsorbance properties of a nematic eutectic mixture doped with a photoactive azo mesogen at room temperature.

The structural transitions in an initially homeotropic bent-rod nematic liquid crystal excited by ac fields of frequency f well above the dielectric inversion point [f.sub.i] are characterized. The studies have shown many new features associated with the secondary instabilities that develop at umbilical sites of the bend Freedericksz (BF) state.

The electric-field-generated effects in the nematic phase of a twin mesogen formed of bent-core and calamatic units, aligned homeotropically in the initial ground state, are examined beyond the dielectric inversion point. The sustained propagative instability is shown to be a novel aspect common to the patterned states.

A photonic switch employing a liquid-crystalline material is proposed. The material exhibits a change in the sign of the dielectric anisotropy switching from a positive to a negative value at a certain crossover frequency.

The anisotropic photocurrent measurements on a binary system of two naphthalene compounds are reported. The results show that there is an anomalous and drastic increase in the value of deltaI, for a particular concentration of the binary system.

The influence of parity and length of the flexible spacer of photoactive liquid-crystalline dimers in a guest host system, on the photoinductive nematic-isotropic transition is studied. It is observed that the odd-even parity of the spacer results in a significant alternation of the magnitude of the photoinduced shift in the nematic-isotropic transition temperature.

Reductive cleavage by using sodium cyanoborohydride in the presence of 1 equiv of boron trifluoride etherate in dry THF can efficiently break the exo C-O bond of the THP ethers furnishing the corresponding alcohols in highly regioselective manner. With this procedure a range of THP ethers are prepared from the corresponding alcohols. All the reactions were clean and completed within 8 hours with good yield of the corresponding alcohols. This is a simple and efficient nonhydrolytic method for the removal of the THP protecting group.

In the present work we have carried out frequency and temperature dependent dielectric studies of an optically active dimeric compound, 4-n-undecyloxy-4'-(cholesteryloxycarbonyl-1-butyloxy)chalcone which shows wide temperature range twist grain boundary (TGB) phases namely TGBA and TGBC*. Dielectric permittivities and DC conductivities have been determined along and normal to the TGB helix axes. Two weak collective modes of dielectric relaxations have been detected for the planar oriented sample where permittivity is measured normal to the long axes of the molecules (but along the TGB helix axis). One mode, which exists in the MHz region, has behavior similar to those of the soft mode due to the amplitude fluctuation. The second one exists in the low frequency region (∼100 Hz) and appears due to phase fluctuation as happens in the case of Goldstone mode. Sample confined between electrodes treated for the homeotropic alignment (permittivity measured normal to the helix axis) does not show any mode of relaxation in the frequency range of 1 Hz to 1 MHz. Measured permittivities suggest negative dielectric anisotropy for the system. [ABSTRACT FROM AUTHOR]