Microrheology in tumbling nematics of 8CB liquid crystals

TL;DR

This study uses particle tracking microrheology to analyze the tumbling behavior of the nematic director in 8CB liquid crystals, revealing structural influences and phase-dependent viscosity changes.

Contribution

It provides new insights into the physical origin of tumbling director motion and differentiates structural phases based on rheological properties in 8CB liquid crystals.

Findings

Identified the dependence of $G'$ on frequency in different phases.

Observed viscosity crossover near the smectic A phase.

Redefined the precessional motion of the nematic director.

Abstract

Particle tracking passive microrheology in 8CB liquid crystals is used to redefine the precessional motion of the orientation of nematic director in liquid crystals. Physical origin of tumbling director in presence of presmectic clusters under zero shear conditions is discussed. Different structural properties (pure nematic phase, presmectic(smectic C and smectic A clusters)) were differentiated with characteristic dependence of $G'$ on $\omega$ in the nematic phase of 8CB liquid crystals. Also, dynamic viscosity is observed with a cross over between parallel and perpendicular components as the smectic A phase is approached.