Magnetic segregation effect in liquid crystals doped with carbon nanotubes.

Danil A Petrov,Pavel K Skokov,Dmitriy V Makarov,Alexander N Zakhlevnykh

doi:10.3762/bjnano.10.145

Abstract

We study the orientational transitions in a suspension of carbon nanotubes in a nematic liquid crystal induced by an external magnetic field. The case of a finite orientational anchoring of liquid crystal molecules at the surface of doped carbon nanotubes is considered. It is shown that in a magnetic field the initial homogeneous planar texture of the liquid crystal–carbon nanotubes mixture is disturbed in a threshold manner (Fréedericksz transition). The orientational and concentration distributions of the suspension are studied for different values of the magnetic field strength and segregation intensity of the impurity subsystem. The optical phase lag between ordinary and extraordinary rays of light transmitted through a layer of a liquid crystal composite is calculated. The possibility of changing the nature of the Fréedericksz transition from second order to first order is shown. This tricritical behavior is related to the redistribution of the carbon nanotubes (segregation effect) inside the layer.

Highlights

Composites of liquid crystals (LCs) and nanoparticles are actively studied systems in soft condensed matter physics, since they successfully combine fluidity and orientational order with specific properties of impurity particles, such as ferromagnetic, ferroelectric, metallic or dielectric impurities [1,2,3,4,5,6,7,8,9,10]
We present the results of numerical calculation of the orientation and concentration profiles of the nematic liquid crystals (NLCs)-Carbon nanotubes (CNTs) mixture and its magneto-optical response
Analysis of the solutions of Equation 16 shows that the homeotropic phase can exist only under the condition of weak anchoring between the NLC matrix and the CNTs for σ ≤ σm, where

Summary

Introduction

Composites of liquid crystals (LCs) and nanoparticles are actively studied systems in soft condensed matter physics, since they successfully combine fluidity and orientational order with specific properties of impurity particles, such as ferromagnetic, ferroelectric, metallic or dielectric impurities [1,2,3,4,5,6,7,8,9,10]. Equation 3–Equation 6, under the conditions of rigid planar anchoring of the NLC director n on the boundaries of the layer allow us to determine the equilibrium spatial distributions of the volume fraction of CNTs g(ζ), and the angles φ(ζ) and ψ(ζ) of the orientations of the NLC and CNTs directors.

Results

Conclusion