PHYSICAL JOURNAL E E®ect of aerosil dispersions on the nematic-to-isotropic interface

Abstract. The e®ect of silica aerosils on the kinetics of the ¯rst-order nematic-isotropic (NI) phase transi-tion is phenomenologically described in the framework of the time-dependent Landau-Ginzburg equation. A steady-state solution to the equation is presented such that the NI interface may propagate with a solitary-like wave pro¯le under constant quenching. The results provide a plausible basis for the interpre-tation of the dynamical e®ects of quenched disorder in the liquid-crystal systems, caused by randomly interconnected porous media, such as aerosils. In the low silica aerosil s ( · 0:1 g=cm 3) regime, the cal-culated values of the interface velocity v(T; s), the interface thickness ·(T; s), and the critical radius of a spherical nucleus of new nematic phase in a bulk isotropic environment, composed of polar molecules, such as 4-n-octyl-40-cyanobiphenyl and 4-n-heptyl-40-cyanobiphenyl shows that the e®ect of silica aerosils on the kinetics is re°ected in a shifting of the set of temperature-dependent curves to lower temperature values. PACS. 61.30.Cz Molecular and microscopic models and theories of liquid crystal structure { 61.30.-v Liquid crystals { 64.70.Md Transitions in liquid crystals