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Title: Smectic Liquid Crystals in an Anisotropic Random Environment

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930671
Report Number(s):
BNL-81170-2008-JA
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review E: Stat. Phys., Plasmas, Fluids; Journal Volume: 75
Country of Publication:
United States
Language:
English
Subject:
national synchrotron light source

Citation Formats

Liang,D., and Leheny, R.. Smectic Liquid Crystals in an Anisotropic Random Environment. United States: N. p., 2007. Web. doi:10.1103/PhysRevE.75.031705.
Liang,D., & Leheny, R.. Smectic Liquid Crystals in an Anisotropic Random Environment. United States. doi:10.1103/PhysRevE.75.031705.
Liang,D., and Leheny, R.. Mon . "Smectic Liquid Crystals in an Anisotropic Random Environment". United States. doi:10.1103/PhysRevE.75.031705.
@article{osti_930671,
title = {Smectic Liquid Crystals in an Anisotropic Random Environment},
author = {Liang,D. and Leheny, R.},
abstractNote = {},
doi = {10.1103/PhysRevE.75.031705},
journal = {Physical Review E: Stat. Phys., Plasmas, Fluids},
number = ,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • We report a high-resolution x-ray scattering study of the smectic liquid crystal octylcyanobiphenyl (8CB) confined to aligned colloidal aerosil gels. The aligned gels introduce orientational fields that promote long-range nematic order while imposing positional random fields that couple to the smectic density wave and disrupt the formation of an ordered smectic phase. At low densities of aerosil, the low-temperature scattering intensity is consistent with the presence of a topologically ordered XY Bragg glass phase that is predicted to form in response to such anisotropic quenched disorder. The observed features of the phase include an algebraic decay of the smectic correlations,more » which is truncated at large length scales due to the imperfect nematic order, and a power-law exponent that agrees closely with the universal value predicted for the XY Bragg glass. At higher aerosil densities, deviations from the XY Bragg glass form are apparent. At high temperature, the scattering intensity displays pretransitional dynamic fluctuations associated with the destroyed nematic to smectic-A transition. The fluctuations obey quasicritical behavior over an extended range of reduced temperature. The effective critical exponents for the correlation lengths and smectic susceptibility differ systematically from those of pure 8CB, indicating that coupling of the nematic order to the gel suppresses its role in the smectic critical behavior.« less
  • No abstract prepared.
  • Experimentally high-resolution ac calorimetry measurments on a liquid-crystal compound exhibiting a smectic-A - smectic-C (SmA-SmC) phase transition which is shown to be mean-field-like is presented. In the light of this experimental result, a simple and convincing argument, based on the mean-field theory, is given to explain why non-mean-field critical exponents were obtained in many of the studies on the SmA-SmC transition. The theory not only gives an excellent fit to the data for temperatures below the transition temperature but also provides a qualitative prediction on the size of the deviation from the linear relationship between (T/sub c/-T) and the squaremore » of the order parameter. The predicted deviation is consistent with x-ray measurements on the order parameter of another liquid-crystal compound.« less
  • Kondo [ital et] [ital al]. [Jpn. J. Appl. Phys. 22, L43 (1983)] discovered that both the smectic-[ital C] and smectic-[ital C][sup *] phases in the liquid crystal [ital p]-[ital n]-decyloxybenzylidene-[ital p]-amino-2-methylbutyl-cinnamate are reentrant with temperature for a range of electric fields. We show that the Landau theory with no adjustable parameters provides a semiquantitative explanation of the phase diagram. The double reentrance is due to two fourth-order terms, one chiral and the other achiral, and is intimately related to the maximum in the pitch, unlike the reentrance under magnetic field. The Sm-C--Sm-C[sup *] transition curve displays both main types ofmore » second-order phase transition, instability, and nucleation, separated by a first-order segment. [ital p]-azoxy-cinnamate-methyl-2-butanol and other compounds with divergent pitch should also show the double reentrance, but the physical origin is different.« less
  • A detailed x-ray scattering and high-resolution ac calorimetric study has been carried out near the smectic-A to chiral smectic-C phase transition of liquid-crystal compounds 4-(2-methyl butyl) phenyl 4-n-octylbiphenyl-4-carboxylate (CE8) and p-(n-decyloxy) benzylidene-p-amino-(2-methylbutyl) cinnamate (DOBAMBC) confined in hydrophilic and hydrophobic aerosil nanoparticle networks. The character of the transition, which is mean field near a tricritical point in bulk, is changed dramatically with an increase of aerosil-induced disorder. X-ray measurements revealed pretransitional behavior and compression of the smectic layers, phenomena that are strongly pronounced in high aerosil concentrations. A theoretical model that takes into account the interplay of relevant mechanisms is proposedmore » to explain the observed phenomena. The effect of chirality on the interaction of liquid crystals with aerosils is discussed.« less