skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Structures and orientational transitions in thin smectic films of tilted hexatic

Abstract

We present detailed systematic studies of structural transformations in thin liquid crystal films with the transition from the smectic-C (SmC) to hexatic (HSmB) phase. For the first time, all possible structures reported in the literature are observed for one material (5O.6) with varying temperature and thickness. In unusual modulated structures, the equilibrium period of stripes is twice the domain size. We interpret these patterns in the framework of a phenomenological Landau-type theory, as equilibrium phenomena produced by a natural geometric frustration in a system having spontaneous splay distortion.

Authors:
; ; ;  [1];  [2];  [3]
  1. Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation)
  2. Institute of Chemical Reactants and Especially Pure Substances (IREA) (Russian Federation)
  3. Laue-Langevin Institute (France), E-mail: kats@ill.fr
Publication Date:
OSTI Identifier:
21067707
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Experimental and Theoretical Physics; Journal Volume: 102; Journal Issue: 4; Other Information: DOI: 10.1134/S1063776106040108; Copyright (c) 2006 Nauka/Interperiodica; Article Copyright (c) 2006 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; EQUILIBRIUM; FILMS; LIQUID CRYSTALS; PHASE TRANSFORMATIONS; THICKNESS

Citation Formats

Dolganov, P. V., Belov, K. I., Dolganov, V. K., Demikhov, E. I., Bolotin, B. M., and Kats, E. I.. Structures and orientational transitions in thin smectic films of tilted hexatic. United States: N. p., 2006. Web. doi:10.1134/S1063776106040108.
Dolganov, P. V., Belov, K. I., Dolganov, V. K., Demikhov, E. I., Bolotin, B. M., & Kats, E. I.. Structures and orientational transitions in thin smectic films of tilted hexatic. United States. doi:10.1134/S1063776106040108.
Dolganov, P. V., Belov, K. I., Dolganov, V. K., Demikhov, E. I., Bolotin, B. M., and Kats, E. I.. Sat . "Structures and orientational transitions in thin smectic films of tilted hexatic". United States. doi:10.1134/S1063776106040108.
@article{osti_21067707,
title = {Structures and orientational transitions in thin smectic films of tilted hexatic},
author = {Dolganov, P. V. and Belov, K. I. and Dolganov, V. K. and Demikhov, E. I. and Bolotin, B. M. and Kats, E. I.},
abstractNote = {We present detailed systematic studies of structural transformations in thin liquid crystal films with the transition from the smectic-C (SmC) to hexatic (HSmB) phase. For the first time, all possible structures reported in the literature are observed for one material (5O.6) with varying temperature and thickness. In unusual modulated structures, the equilibrium period of stripes is twice the domain size. We interpret these patterns in the framework of a phenomenological Landau-type theory, as equilibrium phenomena produced by a natural geometric frustration in a system having spontaneous splay distortion.},
doi = {10.1134/S1063776106040108},
journal = {Journal of Experimental and Theoretical Physics},
number = 4,
volume = 102,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2006},
month = {Sat Apr 15 00:00:00 EDT 2006}
}
  • We report a synchrotron x-ray study of the stacked hexatic smectic-{ital F} phase and the smectic-{ital F} (Sm-{ital F}){r_arrow}smectic-{ital C} (Sm-{ital C}) phase transition in {similar_to}200 and {similar_to}60 molecular layer thick films of terephthal-bis-(20)-alkylanilines. A diffraction geometry is developed to facilitate the measurements on freely suspended liquid-crystal films. Deep in the hexatic Sm-{ital F} phase, both films show a high degree of orientational order. The effects of the surface ordering field in thin liquid-crystal films are discussed. In both samples, the phase transition from the Sm-{ital F} phase to the Sm-{ital C} phase is strongly first order, in contrast withmore » the continuous Kosterlitz-Thouless hexatic-isotropic phase transition predicted for two-dimensional systems.« less
  • X-ray-diffraction studies of the structures and phase transitions of the tilted hexatic phases (smectic F and smectic I) in thin liquid-crystal films of 4-n-heptyloxybenzylidene-4-n-heptylaniline (7O.7) are reported. The measured correlation lengths were strongly anisotropic in both phases. The smectic-I to smectic-F transition is first order as expected from the symmetry change. The smectic-F to smectic-G transition is first order with strong pretransition effects and becomes nearly second order as the film thickness is decreased.
  • Thermal and structural studies have been performed on thin films of {ital n}-heptyl-4{prime}-{ital n}-pentyloxylbiphenyl-4-carboxylate (75OBC). Similar to 65OBC, a surface hexatic phase is observed for films greater than four molecular layers in thickness. Four- and three-layer films display a single, two-dimensional liquid-hexatic transition. The four-layer heat-capacity anomaly is described well by a divergent power-law expression. The three-layer heat-capacity anomaly is qualitatively the same, although its size is greatly reduced. Also, a surface crystal-{ital E} phase is observed immediately below the liquid-hexatic transition(s).
  • We study kinetically controlled orientational and structural transitions of molecular thin films during growth in situ and in real time, using diindenoperylene (DIP) as an example. By time-resolved surface-sensitive x-ray scattering (out of plane and in plane), we follow the organic molecular beam deposition of DIP on silicon oxide, on stepped sapphire, and on rubrene as an organic model surface. We identify transitions for the few-monolayer (ML) regime, as well as for thick (several 10's of ML) films. We show that the differences in the interaction of DIP with the substrate change the thickness as well as temperature range ofmore » the transitions, which include (transient) strain, subtle changes of the orientation, as well as complete reorientation. These effects should be considered rather general features of the growth of organics, which, with its orientational degrees of freedom, is qualitatively different from growth of inorganics.« less