Impact of Weak Nanoparticle Induced Disorder on Nematic Ordering

Abstract

Dilute mixtures of nanoparticles (NPs) and nematic liquid crystals (LCs) are considered. We focus on cases where NPs enforce a relatively weak disorder to the LC host. We use a Lebwohl-Lasher semi-microscopic-type modeling where we assume that NPs effectively act as a spatially-dependent external field on nematic spins. The orientational distribution of locally favoured “easy” orientations is described by a probabilistic distribution function P. By means of a mean field-type approach, we derive a self-consistent equation for the average degree of nematic uniaxial order parameter S as a function of the concentration p of NPs, NP-LC coupling strength and P. Using a simple step-like probability distribution shape, we obtain the S(p) dependence displaying a crossover behaviour between two different regimes which is in line with recent experimental observations. We also discuss a possible origin of commonly observed non-monotonous variations of the nematic-isotropic phase temperature coexistence width on varying p.

Exploring Quantum Dots Size Impact at Phase Diagram and Electrooptical Properties in 8CB Liquid Crystal Soft-Nanocomposites

“…Our current results on the disorder induced by NPs align with previous experimental observations in other systems [41] and a previous investigation in -type systems [43]. Moreover, they are consistent with theoretical predictions [42]. QDs introduce deformations in the nematic director field due to their interaction with the mesogenic molecules.…”

“…At high enough concentrations, the QDs interact with each other through the elastic distortion of the orientational field, and in some cases, translational order emerges, forming colloidal crystals [43]. Since the distortion of the nematic field induces variations in the tensorial order parameter [42], it consequently leads to changes in the properties of the nematic host.…”

“…A few years ago, we conducted a study on the impact of CdSe/ZnS core-shell QDs on the nematic order of the LC compound 4-n-pentyloxyphenyl-4 -n-octyloxybenzoate (5OO8) [41,42]. It was evidenced that the NPs can reduce the orientational order parameter.…”

‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline Material

“…For the non-oriented 5CB sample, the supercooling below T m was possible, and the mentioned tendency for ε || (T) qualitatively changed: the notable decrease of the value of ε N (T) is visible. In the opinion of the author, the link of this phenomenon to the growing impact of topological defects distorting the uniaxial arrangement can be indicated [42]. Such a possibility can show experimental studies and related modeling for 5CB + nanoparticles composites [20,21].…”

A High-Resolution Terahertz Electric Field Sensor Using a Corrugated Liquid Crystal Waveguide

“…On the other hand, there have been many reports in recent years on nematic liquid crystals (LCs) [26,27], which are very sensitive to aspects of the external environment such as lights [28], electric fields [29], magnetic fields [30], and temperature [31][32][33]. Wang et al proposed an optical temperature sensor based on a silicon nitride micro-ring resonator incorporating LC cladding [34].…”