Diffusivity Maximum in a Reentrant Nematic Phase

Stieger, Tillmann; Mazza, Marco G.; Schoen, Martin

doi:10.3390/ijms13067854

Cited by 5 publications

(3 citation statements)

References 61 publications

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“…The simulations are performed for up to N = 30 000 molecules using the Gay-Berne-Kihara potential [24], which models the liquid crystal molecules as spherocylindrical soft particles possessing anistropic interactions. The potential is known [25,26] to generate a smectic-A phase for appropriate parameter settings. The simulation protocol is described in the Supplemental Material [27].…”

Section: -2mentioning

confidence: 99%

Single-molecule diffusion in freely suspended smectic films

2014

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We present a study of the molecular diffusion in freely suspended smectic-A liquid crystal films with thicknesses ranging from 20 down to only two molecular layers. The molecular mobility is directly probed by determining the trajectories of single, fluorescent tracer molecules. We demonstrate, using several different smectic compounds, that a monotonic increase of the diffusion coefficient with decreasing film thickness is a general phenomenon. In two-layer films, the diffusion is enhanced by a factor of 3 to 5 compared to the corresponding bulk smectic phase. Molecular dynamics simulations of freely suspended smectic films are presented which support the experimental results.

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Section: -2mentioning

confidence: 99%

Single-molecule diffusion in freely suspended smectic films

2014

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“…Three-dimensional periodic boundary conditions are often used in such simulations to represent a bulk state, but they sometimes induce serious artifacts in chiral phases due to inappropriate periodic images, unless the box length along the twisted axis is an integer of half the pitch distance. In this work, therefore, we used solid substrates with planar anchoring [ 38 , 60 , 61 ] along the axis of helical rotation in order to break symmetry and eliminate boundary artifacts in that axis. The fluid-substrate potential energy is expressed as

where

is the depth of the attractive well and

is the perpendicular distance between molecule i and the lower substrate.…”

Section: Methodsmentioning

confidence: 99%

Effect of Central Longitudinal Dipole Interactions on Chiral Liquid-Crystal Phases

Nozawa

Brumby

Yasuoka

2018

IJMS

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Monte Carlo simulations of chiral liquid-crystals, represented by a simple coarse-grained chiral Gay–Berne model, were performed to investigate the effect of central longitudinal dipole interactions on phase behavior. A systematic analysis of the structural properties and phase behavior of both achiral and chiral systems, with dipole interactions, reveals differing effects; strong dipole interactions enhance the formation of layered structures; however, chiral interactions may prevent the formation of such phases under certain conditions. We also observed a short-ranged smectic structure within the cholesteric phases with strong dipole interactions. This constitutes possible evidence of presmectic ordering and/or the existence of chiral line liquid phases, which have previously been observed in X-ray experiments to occur between the smectic twisted grain boundary and cholesteric phases. These results provide a systematic understanding of how the phase behavior of chiral liquid-crystals changes when alterations are made to the strength of dipole interactions.

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“…For example, Goto et al showed increase of charge mobility in the nematic phase of LCs [7,8]. Recently, other computer simulation studies revealed that nonpolar LCs, exhibiting a reentrant nematic (RN) phase, can show enhanced rates of translational mobility [9][10][11][12]. This finding was attributed to the lowering of the rotational configurational entropy upon forming a denser RN phase.…”

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confidence: 98%

Experimental evidence of enhanced transport in supernematics

Kipnusu,

Zeigermann,

Iacob

et al. 2014

Preprint

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Deviations of molecular shapes from spherical symmetry may give rise to a variety of novel phenomena, including their dynamic behavior. It has recently been predicted [Mazza et al. Phys. Rev. Lett. 105, 227802 (2010)] that liquid crystals in the reentrant nematic phases may show unexpectedly high rates of translational displacements. Using broadband dielectric spectroscopy and a single-component thermotropic liquid crystal we explore molecular dynamics in the vicinity of the reentrant nematic transition and find the formation of a maximum in the mobilities upon changing temperature. The occurrence of the high mobility states are found to be history-dependent due to the formation of metastable mesophases on heating. The experimental results are further supported by computer simulation. Our results contribute to the clarification of an ongoing controversy on the dynamics of reentrant nematics.

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Diffusivity Maximum in a Reentrant Nematic Phase

Cited by 5 publications

References 61 publications

Single-molecule diffusion in freely suspended smectic films

Single-molecule diffusion in freely suspended smectic films

Effect of Central Longitudinal Dipole Interactions on Chiral Liquid-Crystal Phases

Experimental evidence of enhanced transport in supernematics

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