Light-induced layer by layer thickening in photosensitive liquid crystal membranes

Photosensitive smectic membranes of pure liquid crystal (LC) were studied under white light illumination. A thickness increase is observed in the illuminated film area. Appropriate light and thermal conditions lead to a thickening layer by layer process. This unusual phenomenon is opposite to the well-known step-by-step thinning transitions under heating. We give a phenomenological interpretation for thickening based on layer transport of LC matter towards the illuminated area.     

Temperature-and field-induced transitions in free-standing films of an antiferroelectric liquid crystal

Thin free-standing films of a compound with the smectic-C _A ^* and smectic-C _α ^* phases were investigated by means of depolarized microscopy and optical reflectivity. In thin films, the smectic phase sequence C _A ^* ?C_α/*?A is replaced by a series of temperature-and field-induced transitions into states with the coplanar orientation of molecular tilt planes. Transitions are accompanied by a change in the direction of the electric polarization with respect to the tilt plane of molecules. The coplanar structure of these states is consistent with the Ising model.     

Polar smectic subphases: Phase diagrams, structures and X-ray scattering

We analyze a discrete phenomenological model accounting for phase transitions and structures of polar Smectic-C* liquid-crystalline phases. The model predicts a sequence of phases observed in experiment: antiferroelectric SmC _A ^* –ferrielectric SmC _FI1 ^* –antiferroelectric SmC _FI2 ^* (three-and four-layer periodic, respectively)–incommensurate SmC _α ^* –SmA. We find that, in the three-layer SmC _FI1 ^* structure, both the phase and the module of the order parameter (tilt angle) differ in smectic layers. This modulation of the tilt angle (and therefore of the layer spacing d) must lead to X-ray diffraction at the wave vectors Q _s =2πs/d(s=n±1/3) even for the nonresonant scattering.     

Experimental indication of macroscopic polarization parallel to the tilt plane in free-standing films of ferroelectric liquid crystals 8SI* and DOBAMBC

Optical reflectivity and x-ray studies have been conducted on free-standing films and bulk samples of ferroelectric liquid crystals near the smectic-A-smectic-C ^* transition. A tilt plane rotation with respect to the direction of an applied electric field is found in the ferroelectric films above the bulk transition temperature. Whereas the macroscopic polarization is perpendicular to the tilt plane at low temperature, it is parallel to the tilt plane at elevated temperature. The temperature dependence of the average tilt angle is measured. Zh. éksp. Teor. Fiz. 116, 1329–1334 (October 1999) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

Laws of formation of polar smectic phases under a frustrated interaction

The Landau theory of phase transitions with a two-component order parameter is used to systematically calculate the structures and phase diagrams of polar liquid crystals. Commensurate and incommensurate structures with a layer-type period form as a result of a frustration interaction. Phase diagrams are calculated when various short- and long-range interlayer interactions are sequentially introduced. As a result, the nature of formation of various structures is revealed. The calculated phase diagrams explain the formation of various phases, their temperature sequence (including so-called “unusual” sequence of phases), and the nature of forces responsible for the formation of a certain structure and the shape of a phase diagram.     

Optical reflectivity study of synclinic and anticlinic structures in thin freely suspended smectic films

Optical reflectivity studies have been conducted on freely suspended films with synclinic and anticlinic structures. For the first time quantitative data were obtained on orientational ordering in films with anticlinic structure. In the same wide temperature range of more than 30 K we observed both transverse and longitudinal ferroelectricity in the films of the same thickness. Equilibrium transition temperatures between structures with transverse and longitudinal polarization were above the bulk transition temperature to the SmC phase. The molecule tilt was determined in superthin films with synclinic and anticlinic ordering. Received 29 October 1999 and Received in final form 17 February 2000     

Electrochemical,Spectroscopic, and Quantum Chemical Study of Electrocatalytic Hydrogen Evolution in the Presence of N-Methyl-9-phenylacridinium Iodide

Russian Journal of Organic Chemistry - Main intermediates in the electrocatalytic hydrogen evolution promoted by N-methyl-9-phenyl-acridinium iodide have been identified and characterized using...     

Coalescence of Islands of Different Thicknesses in Smectic Nanofilms

JETP Letters - In smectic nanofilms, the coalescence of islands (areas thicker than the smectic nanofilm) of different thicknesses and radial dimensions is studied. The initial stage of coalescence...     

Two-dimensional ordering of inclusions in smectic C phase

The organization of inclusions nucleated in free standing films of smectic C (SmC) liquid crystal is investigated using polarized light microscopy. Anchoring on the inclusion boundaries induces distortions of the in-plane orientational order of the SmC phase, which drive the elastic interactions between inclusions. Such interactions show a quadrupolar character. At low concentration, the inclusions self-organize in linear or branched chain structures, while at high concentrations two-dimensional patterns appear in the film.     

Influence of the nature of organic components in dinuclear copper(II) pivalates on the composition of thermal decomposition products

Tetrabridged dinuclear complexes ((2-NH₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (2·С₆Н₆) and ((3-NH₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (3) and the cocrystallization product ((4-NMe₂)C₅H₄N)₂Cu(η²–OOCCMe₃)₂·2((4-NMe₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (4) were synthesized by the reaction of the polymer [Cu(OOCCMe₃)₂]_n (1) with aminopyridine ligands (L) of different nature (Cu: L = 1:1) in С₆Н₆. The solid-state thermal decomposition of these compounds was studied by differential scanning calorimetry and thermogravimetry, and their electrochemical behavior was investigated by cyclic voltammetry. All newly synthesized complexes were studied by X-ray diffraction, the magnetic properties of the complexes were investigated, and ESR measurements were performed.