Smectic ordering in liquid crystal - aerosil dispersions II. Scaling analysis

TL;DR

This paper investigates how quenched random disorder from aerosil gels affects smectic order in liquid crystals, focusing on finite-size effects and scaling behavior in the 8CB+aerosil system.

Contribution

It provides a detailed analysis of finite-size scaling and two-scale universality in liquid crystal-aerosil dispersions, extending previous calorimetric and x-ray studies.

Findings

Pseudo-critical scaling behavior observed in 8CB+aerosil system

Finite-size effects influence smectic order in the presence of aerosil gels

QRD strength varies with aerosil density

Abstract

Liquid crystals offer many unique opportunities to study various phase transitions with continuous symmetry in the presence of quenched random disorder (QRD). The QRD arises from the presence of porous solids in the form of a random gel network. Experimental and theoretical work support the view that for fixed (static) inclusions, quasi-long-range smectic order is destroyed for arbitrarily small volume fractions of the solid. However, the presence of porous solids indicates that finite-size effects could play some role in limiting long-range order. In an earlier work, the nematic - smectic-A transition region of octylcyanobiphenyl (8CB) and silica aerosils was investigated calorimetrically. A detailed x-ray study of this system is presented in the preceding Paper I, which indicates that pseudo-critical scaling behavior is observed. In the present paper, the role of finite-size scaling and two-scale universality aspects of the 8CB+aerosil system are presented and the dependence of the QRD strength on the aerosil density is discussed.