Jozef Zmija

Determination of molecular parameters of the MHPB(H)PBC and MHPB(F)PBC antiferroelectric liquid crystals

Abstract Two investigated antiferroelectric liquid crystals, MHPB(H)PBC and MHPB(F)PBC, were synthesized [1] and some their physical properties were described earlier [2]. Apart of the above, MHPB(H)PBC and MHPB(F)PBC have been studied by means of dielectric, densitometric, refractometric and X-ray measurements. Spontaneous polarization P s and tilt angle θ in ferro- (SmC*) and antiferroelectric (SmCA*) phases of MHPB(H)PBC and MHPB(F)PBC have also been investigated. Transverse α1 and longitudinal α1 molecular polarizabilities have been calculated from the ordinary n 0 and extraordinary n e refractive indices and density ρ of MHPB(H)PBC and MHPB(F)PBC, using Neugebauers, Vuks and Lorentz equations with both Haller and Subramhanyama extrapolation procedures. Effective values of the molecular dipole moment μ have been calculated from electric permittivity ε in the 1 phases of these compounds, using Maier and Meier equation.

Influence of Quadrupolar Ordering Factor on Supermolecular Structure in Ferroelectric Sm C

Abstract We have synthesized the compound: 2-methylbutyl-4-n-nonanoyloxybiphenyl-4′-carboxylate (MBOBC). MBOBC shows the inversions in the sign of the spontaneous polarization, what was first reported by Goodby et al.[1] and Eidenschink et al.[2]. This ferroelectric liquid crystals has been studied by dielectric, densytometric, refractometric an X-ray measurements. After comparing the PS taken from experiment and obtained from theoretical approximation[3,4,5], the contribution of the dipolar a1 and quadrupolar a2 terms in the rotational potential have been estimated.

Determination of the Hindered Rotation Degree of Chiral Molecules Around Their Long Molecular Axes in the Sc* Phase of 4-(2‘-Methylbutyl)-4‘-n-Octylbiphenyl-4-Carboxylate

Abstract Chiral 4-(2“-methylbutyl)-phenyl-4‘-octylbiphenyl-4-carboxylate (CE8) has been studied by dielectric, densytometric, refractic and X-ray measurements. On the basis of these measurements the effective value of the molecular dipole moment (μ), the angle between the vector of the molecular dipole moment and the long axis of molecule (γ) as well as the transverse (α1) and longitudinal (α1) molecular polarizabilities have been calculated8. In addition the sign and the magnitude of spontaneous polarization (Ps), the tilt angle (6) and the helical pitch (λ) have been measured for the same liquid crystal CE8. Knowing the molecular parameters μ, γ, α, α1 and Θ from the experiment and the molecular structure from computer investigation, the spontaneous polarization Ps has been calculated as the vector sum of the components of molecular dipole moments μ perpendicular to the tilt direction. To do it the rotational potential given by B.Zeks2 has been used. According to this approximation the measured spontane...

Holographic grating formation mechanism in dye-doped nematic liquid crystal thin layer under dc electric field

Mechanism of holographic dynamic grating recording in a thin cell with dye doped nematic liquid crystal under laser light has been proposed. Nematic liquid crystal with dye is sandwiched between two coating glass plates covered by ITO conductive and polyimide orientation layers. In this experiment, two interfering laser beams induced spatial modulation of refraction index and form interference pattern in the liquid crystal cell. The recording mechanism is linked with DC electric field driven reorientation of nematic director and induces the bulk photoconductivity of the system.

Dosimetric properties of activated lithium tetraborate

This paper describes preliminary investigations of Li2B4O7 thermoluminescent phosphors as candidates for gamma radiation dosimetry materials. Single crystals, glasses, and polycrystals of lithium tetraborate activated with different dopants have been investigated.

The Effect of Terminal Substituents on the Molecular Dipole Moments of Liquid Crystalline 4-(Trans-4′-n-Alkylcyclohexyl) Benzoates

Abstract The dielectric constants (e∥ and e⊥) of aryl 4- (trans-4′-n-alkylcyclohexyl)benzoates have been determined The influence of the substituents on the dipole moment of the investigated esters has been discussed.

Liquid Crystal Elements of Laser Optics. The Optical Isolator

Abstract The studies have been done on the possibility of liquid crystals application for the optical isolation of laser systems. Tie appropriate elements containing different mesogenic materials have been made. The results suggest that these elements are very useful in laser systems.

Diamagnetic anisotropy and splay and bend elastic constants of 4-trans-n-hexyl-cyclohexyl-isothiocyanatobenzene (6CHBT)

We have measured the dielectric constants of 6CHBT. The results of the studies for different alignment and thicknesses under different electric measuring fields and magnetic fields are presented. We discuss how dielectric properties depend on boundary condition, thicknesses of the samples, and magnitudes of electric and magnetic fields. The obtained experimental results and the discussion in the terms of continuum theory make it possible to compute the diamagnetic anisotropy ((Delta) (Chi)), splay and bend elastic constants (K11, K33) of 6CHBT.

Polymer-dispersed liquid-crystal displays: principles, preparation, properties, and applications

An overview of preparation methods, physical principles, main properties, present and possible applications of polymer dispersed liquid crystals is presented. Special attention is paid to polymer dispersed chiral smectic liquid crystals.

Liquid-crystal materials for STN effect

An influence of material constants such as elastic constants, electric permittivity constants, refractive indices, viscosity and concentration of optical dopants on the performance of STN displays are discussed. It is shown that mixtures containing as main components isothiocyanato and borodioxane compounds are speedily operating liquid crystalline materials and a high multiplexing level in this mode is obtained.