X-ray scattering study of smectic ordering in a silica aerogel
- Condensed Matter Laboratory, Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States) Dipartimento di Elettronica, Universita di Pavia, 27100 Pavia (Italy) Exxon Research and Engineering, Annandale, New Jersey 08801 (United States) Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States) Lawrence Livermore Laboratory, Livermore, California 94551 (United States)
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.
- OSTI ID:
- 5446179
- Journal Information:
- Physical Review Letters; (United States), Journal Name: Physical Review Letters; (United States) Vol. 71:21; ISSN 0031-9007; ISSN PRLTAO
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360602* -- Other Materials-- Structure & Phase Studies
661300 -- Other Aspects of Physical Science-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COHERENCE LENGTH
COHERENT SCATTERING
CONFINEMENT
CRYSTALS
DIFFRACTION
DIMENSIONS
DOMAIN STRUCTURE
FLUIDS
LENGTH
LIQUID CRYSTALS
LIQUIDS
MATERIALS
ORDER-DISORDER TRANSFORMATIONS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POROUS MATERIALS
SCATTERING
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
X-RAY DIFFRACTION