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First order isotropic - smectic-A transition in liquid crystal-aerosil gels

M. K. Ramazanoglu·P. S. Clegg·R. J. Birgeneau·C. W. Garland·M. E. Neubert·J. M. Kim
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Abstract

The short-range order which remains when the isotropic to smectic-A transition is perturbed by a gel of silica nanoparticles (aerosils) has been studied using high-resolution synchrotron x-ray diffraction. The gels have been created \textit{in situ} in decylcyanobiphenyl (10CB), which has a strongly first-order isotropic to smectic-A transition. The effects are determined by detailed analysis of the temperature and gel density dependence of the smectic structure factor. In previous studies of the continuous nematic to smectic-A transition in a variety of thermotropic liquid crystals the aerosil gel appeared to pin, at random, the phase of the smectic density modulation. For the isotropic to smectic-A transition the same gel perturbation yields different results. The smectic correlation length decreases more slowly with increasing random field variance in good quantitative agreement with the effect of a random pinning field at a transition from a uniform phase directly to a phase with one-dimensional translational order. We thus compare the influence of random fields on a \textit{freezing} transition with and without an intervening orientationally ordered phase.

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M. K. Ramazanoglu, P. S. Clegg, R. J. Birgeneau, C. W. Garland, M. E. Neubert, J. M. Kim. 2003-11-27. First order isotropic - smectic-A transition in liquid crystal-aerosil gels. https://doi.org/10.1103/physreve.69.061706

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