Behavior of the layer compression elastic modulus near, above, and below a smectic C-hexatic I critical point in binary mixtures.
We present the first study of the layer compression modulus B carried out near, above and below the Smectic C-Hexatic I critical point in racemic mixtures of methylbutyl phenyl octylbiphenyl-carboxylate (8SI) and the octyloxy biphenyl analog (8OSI), at frequencies ranging from 0.2 Hz to 2 x 10(3) Hz. The behavior of B as a function of temperature shows a progressive evolution from a first order transition in 8SI to a continuous supercritical behavior in 8OSI. The latter is characterized by an increase in B, which appears above the transition, and which is followed by a leveling off when the temperature is decreased towards the transition. It is proposed that this behavior stems from the relaxation of the hexatic domains which are frozen in the frequency range studied. For the supercritical and near-critical compounds, B exhibits a small dip near the transition temperature, which is visible in the low frequency range only, indicating that the dynamics associated with the critical point is very slow. We also report measurements in the Crystal-J phase of the pure compounds, and show that 8SI behaves mechanically as a hexatic phase and 8OSI as a soft crystal phase.
Rogez
D
D
Laboratoire de Dynamique des Fluides Complexes, UMR n 7506, ULP-CNRS, Université Louis Pasteur 4, rue Blaise Pascal, 67070 Strasbourg Cedex, France.
Benguigui
L G
LG
Martinoty
P
P
Phys Rev Lett. 1987 Aug 31;59(9):1002-1005
10035934
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 1995 May;51(5):4585-4597
9963172
Phys Rev E Stat Nonlin Soft Matter Phys. 2002 Mar;65(3 Pt 1):030702
11909017
Phys Rev Lett. 1986 Jul 7;57(1):98-101
10033367
Phys Rev Lett. 1995 Jan 9;74(2):270-273
10058346
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 1993 Feb;47(2):1184-1198
9960121