Fast linear electrooptic effect in non-chiral bent-core liquid crystal

AbstractElectrooptic phenomena caused by weak electric fields, much lower than those needed for the helix unwinding, in helical smectic liquid crystals were studied in thin planar samples. The investigations were performed in chiral liquid crystal 4-(1-methyl-heptyloxycarbonyl) phenyl 4′-(3-butanoyloxy propyl-1-oxy) biphenyl-4-carboxylate which exhibits antiferro-electric properties. We have found that electric field applied to a helical smectic liquid crystal caused two effects. First, the helix was deformed and the position of effective optic axis changed by an angle proportional to the field strength. The second effect, quadratic in field, causes the change in the shape of the indicatrix. As a consequence, the relative changes in the light intensity caused by external electric field consist of two components. The first component represents the modulation with the fundamental frequency and the second one with the doubled frequency (second harmonic of the electrooptic effect). The ab- solute values of the first- and second-order electrooptic coefficients have been determined and their temperature dependence discussed.

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Electrooptic effect in freely suspended ferroelectric liquid crystal film and its application to a field measurement

Proceedings of 1999 IEEE 13th International Conference on Dielectric Liquids (ICDL'99) (Cat. No.99CH36213) ◽

10.1109/icdl.1999.799020 ◽

2003 ◽

Author(s):

S. Uto ◽

Y. Matsumoto ◽

M. Ozaki ◽

K. Yoshino

Keyword(s):

Liquid Crystal ◽

Field Measurement ◽

Ferroelectric Liquid Crystal ◽

Electrooptic Effect ◽

Crystal Film ◽

Freely Suspended

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Freeze-fracture TEM of the helical smectic A* phase

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012179x ◽

1992 ◽

Vol 50 (1) ◽

pp. 278-279

Author(s):

K.J. Ihn ◽

R. Pindak ◽

J. A. N. Zasadzinski

Keyword(s):

Liquid Crystal ◽

Grain Boundary ◽

Grain Boundaries ◽

Freeze Fracture ◽

Smectic Phase ◽

Layer Spacing ◽

Screw Dislocations ◽

Smectic A ◽

Smectic Phases ◽

Discrete Amount

A new liquid crystal (called the smectic-A* phase) that combines cholesteric twist and smectic layering was a surprise as smectic phases preclude twist distortions. However, the twist grain boundary (TGB) model of Renn and Lubensky predicted a defect-mediated smectic phase that incorporates cholesteric twist by a lattice of screw dislocations. The TGB model for the liquid crystal analog of the Abrikosov phase of superconductors consists of regularly spaced grain boundaries of screw dislocations, parallel to each other within the grain boundary, but rotated by a fixed angle with respect to adjacent grain boundaries. The dislocations divide the layers into blocks which rotate by a discrete amount, Δθ, given by the ratio of the layer spacing, d, to the distance between grain boundaries, lb; Δθ ≈ d/lb (Fig. 1).

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Attractive mode force microscopy of chiral liquid crystal surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121740 ◽

1992 ◽

Vol 50 (1) ◽

pp. 268-269

Author(s):

B.D. Terris ◽

R. J. Twieg ◽

C. Nguyen ◽

G. Sigaud ◽

H. T. Nguyen

Keyword(s):

Liquid Crystal ◽

Crystal Surfaces ◽

Free Surfaces ◽

Control Range ◽

Force Microscopy ◽

Liquid Crystal Films ◽

Chiral Liquid Crystal ◽

Crystal Films ◽

Electrostatic Charging ◽

And Shifts

We have used a force microscope in the attractive, or noncontact, mode to image a variety of surfaces. In this mode, the microscope tip is oscillated near its resonant frequency and shifts in this frequency due to changes in the surface-tip force gradient are detected. We have used this technique in a variety of applications to polymers, including electrostatic charging, phase separation of ionomer surfaces, and crazing of glassy films.Most recently, we have applied the force microscope to imaging the free surfaces of chiral liquid crystal films. The compounds used (Table 1) have been chosen for their polymorphic variety of fluid mesophases, all of which exist within the temperature control range of our force microscope.

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