Nematic-isotropic phase transition: An extended mean field theory

Abstract

The small magnitude of (T, -T )/T"where T, is the nematic-isotropic phase transition temperature and T denotes the virtual transition temperature, has been a long-standing puzzle in the physics of liquid crystals. We show that by extending the mean field theory to include the isotropic, densitydependent component of the molecular interaction the magnitudes of both (T, -T*)/T, and the density change at the transition automatically become in accord with the experimental values. In addition, the theory yields a value of dT, /dp, where p denotes pressure, that is on the same order as the experiment. [4], but the incorporation of that extra part also materially affects the character of the N-I transition.In particular, the predicted magnitude of (T, -T*)/T, is lowered to the experimental range, while at the same time the theory also yields the right magnitudes both for the density variation across the N-I transition as well as for the variation of T, with pressure.

Simulation of Surface-Enhanced Ordering in Smectic Films

“…Experimentally observed surface induced mesophase transitions have been studied mainly for the isotropic/nematic transition series [3][4][5]. The nematic/smectic A and isotropic/smectic surface induced transitions have been studied less [1,[6][7][8][9][10].…”

A perturbed hard-sphere-chain equation of state for nematic liquid crystals and their mixtures with polymers

“…However, the magnitude of exponent m in crystals, however, saturated thermodynamic properties equation ( 12) has been the subject of continuing discusare not readily available at present. In the literature, sion [ 19,30 ]. Exponent m is often adjusted to ® t experionly pV T data are tabulated for a limited number of mental data for the nematic± isotropic transition [ 30].…”

Evidence of Tricritical Behavior at the Nematic Isotropic Transition

“…Reasonable values for the parameters in the phenomenological model lead to values of those ratio which are ten times too large as compared with the experimental results. There have been quite a few works [17][18][19][20] to resolve these puzzling aspects. This work substantiated the claim of Tao et al 18 but the value of (Q * − Q NI )/Q NI was found to be inconsistent with the observed values.…”

“…There have been quite a few works [17][18][19][20] to resolve these puzzling aspects. This work substantiated the claim of Tao et al 18 but the value of (Q * − Q NI )/Q NI was found to be inconsistent with the observed values. In the present work we have showed how the higher order term in the Landau-de Gennes free energy expansion gives the consistent results of (T NI − T * )/T * and (Q * − Q NI )/Q NI .…”