X-ray scattering study of smectic ordering in a silica aerogel

We have studied, via x-ray scattering, the nematic to smectic-[ital A] (NA) translational ordering of the liquid-crystal--forming compound octylcyanobiphenyl (8CB) incorporated into the pores of a silica aerogel. We find that the aerogel dramatically alters 8CB phase behavior, eliminating the NA tra...

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Bibliographic Details
Published in:Physical review letters 1993-11, Vol.71 (21), p.3505-3508
Main Authors: CLARK, N. A, BELLINI, T, MALZBENDER, R. M, THOMAS, B. N, RAPPAPORT, A. G, MUZNY, C. D, SCHAEFER, D. W, HRUBESH, L
Format: Article
Language:English
Subjects:
360602 - Other Materials- Structure & Phase Studies
661300 - Other Aspects of Physical Science- (1992-)
Chemistry
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
COHERENCE LENGTH
COHERENT SCATTERING
Colloidal gels. Colloidal sols
Colloidal state and disperse state
CONFINEMENT
CRYSTALS
DIFFRACTION
DIMENSIONS
DOMAIN STRUCTURE
Exact sciences and technology
FLUIDS
General and physical chemistry
LENGTH
LIQUID CRYSTALS
LIQUIDS
MATERIALS
MATERIALS SCIENCE
ORDER-DISORDER TRANSFORMATIONS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POROUS MATERIALS
SCATTERING
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
X-RAY DIFFRACTION
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Summary:We have studied, via x-ray scattering, the nematic to smectic-[ital A] (NA) translational ordering of the liquid-crystal--forming compound octylcyanobiphenyl (8CB) incorporated into the pores of a silica aerogel. We find that the aerogel dramatically alters 8CB phase behavior, eliminating the NA transition found at [ital T]=[ital T][sub [ital N][ital A]]=33.7 [degree]C in bulk samples and replacing it by a short range smectic ordering having a correlation length which at [ital T][sub [ital N][ital A]] is [xi][similar to]40 A, much smaller than the aerogel pore and nematic domain size [xi][sub [ital p]][similar to]200 A. As [ital T] is lowered this smectic disorder is eliminated from the pores, [xi] increasing continuously over a 20 [degree]C range to saturate at [xi][sub [ital p]] for [ital T][lt][ital T][sub [ital N][ital A]][minus]20 [degree]C.
ISSN:0031-9007
1079-7114
DOI:10.1103/physrevlett.71.3505