Smectic ordering in liquid-crystal–aerosil dispersions. I. X-ray scattering
- 31 January 2003
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review E
- Vol. 67 (1), 011708
- https://doi.org/10.1103/physreve.67.011708
Abstract
Comprehensive x-ray scattering studies have characterized the smectic ordering of octylcyanobiphenyl (8CB) confined in the hydrogen-bonded silica gels formed by aerosil dispersions. For all densities of aerosil and all measurement temperatures, the correlations remain short range, demonstrating that the disorder imposed by the gels destroys the nematic (N) to smectic- transition. The smectic correlation function contains two distinct contributions. The first has a form identical to that describing the critical thermal fluctuations in pure 8CB near the transition, and this term displays a temperature dependence at high temperatures similar to that of the pure liquid crystal. The second term, which is negligible at high temperatures but dominates at low temperatures, has a shape given by the thermal term squared and describes the static fluctuations due to random fields induced by confinement in the gel. The correlation lengths appearing in the thermal and disorder terms are the same and show a strong variation with gel density at low temperatures. The temperature dependence of the amplitude of the static fluctuations further suggests that nematic susceptibility becomes suppressed with increasing quenched disorder. The results overall are well described by a mapping of the liquid-crystal–aerosil system onto a three-dimensional model in a random field with disorder strength varying linearly with the aerosil density.
Keywords
This publication has 30 references indexed in Scilit:
- Hydrogen-bonded silica gels dispersed in a smectic liquid crystal: A random fieldsystemPhysical Review E, 2002
- Universality and Scaling in the Disordering of a Smectic Liquid CrystalScience, 2001
- Effect of silica aerosil dispersions on the dielectric properties of a nematic liquid crystalPhysical Review E, 2001
- Aerosil Dispersed in a Liquid Crystal: Magnetic Order and Random Silica DisorderPhysical Review Letters, 2001
- Effects of quenched disorder on the orientational order of the octylcyanobiphenyl liquid crystalPhysical Review E, 1999
- Calorimetric and small angle x-ray scattering study of phase transitions in octylcyanobiphenyl-aerosil dispersionsPhysical Review E, 1998
- Light-scattering measurement of the nematic correlation length in a liquid crystal with quenched disorderPhysical Review E, 1998
- Dynamic Light Scattering Study of Nematic and Smectic-Liquid Crystal Ordering in Silica AerogelPhysical Review Letters, 1995
- Heat-capacity study of nematic-isotropic and nematic–smectic-Atransitions for octylcyanobiphenyl in silica aerogelsPhysical Review E, 1995
- X-ray scattering study of smectic ordering in a silica aerogelPhysical Review Letters, 1993