Entropy-driven enhanced self-diffusion in confined reentrant supernematics

TL;DR

This study uses molecular dynamics simulations to reveal that confined reentrant nematic liquid crystal phases exhibit significantly enhanced self-diffusion due to decreased rotational entropy, suggesting new experimental avenues.

Contribution

It demonstrates that reentrant nematic phases in nanoconfinement have higher self-diffusivity driven by entropy effects, a novel insight into confined liquid crystal behavior.

Findings

Reentrant nematic phases form at high densities with near-perfect nematic order.

Self-diffusivity in supernematic phases exceeds that in ordinary nematics by an order of magnitude.

Decreased rotational entropy under confinement enhances molecular mobility.

Abstract

We present a molecular dynamics study of reentrant nematic phases using the Gay-Berne-Kihara model of a liquid crystal in nanoconfinement. At densities above those characteristic of smectic A phases, reentrant nematic phases form that are characterized by a large value of the nematic order parameter $S\simeq1$. Along the nematic director these "supernematic" phases exhibit a remarkably high self-diffusivity which exceeds that for ordinary, lower-density nematic phases by an order of magnitude. Enhancement of self-diffusivity is attributed to a decrease of rotational configurational entropy in confinement. Recent developments in the pulsed field gradient NMR technique are shown to provide favorable conditions for an experimental confirmation of our simulations.