Thermotropic Liquid Crystals, Fundamentals

Vertogen, G.; Jeu, Wim H. de

doi:10.1007/978-3-642-83133-1

Cited by 575 publications

(359 citation statements)

References 104 publications

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“…The dipolar alignments are responsible for an increase in the low-temperature Kirkwood factor, g K = 1 + ρ h ∆ (r)dr, ρ is the number density. Despite these long-range orientational correlations, the low-temperature phase does not show any specific orientational order, as confirmed by calculations of the first and second orientational order parameters [54,55] (Fig. 9) as explained below.…”

Section: Dynamic Crossoversupporting

confidence: 64%

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Dynamical and orientational structural crossovers in low-temperature glycerol

2016

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Mean square displacements of hydrogen atoms in glass-forming materials and proteins, as reported by incoherent elastic neutron scattering, show kinks in their temperature dependence. This crossover, known as the dynamical transition, connects two approximately linear regimes. It is often assigned to the dynamical freezing of subsets of molecular modes at the point of equality between their corresponding relaxation times and the instrumental observation window. The origin of the dynamical transition in glass-forming glycerol is studied here by extensive molecular dynamics simulations. We find the dynamical transition to occur for both the center of mass translations and the molecular rotations at the same temperature, insensitive to changes of the observation window. Both the translational and rotational dynamics of glycerol show a dynamic crossover from the structural to a secondary relaxation at the temperature of the dynamical transition. A significant and discontinuous increase in the orientational Kirkwood factor and in the dielectric constant is observed in the same range of temperatures. We, however, do not find any indications of a true thermodynamic transition to an ordered low-temperature phase. We therefore suggest that all observed crossovers are dynamic in character. The increase in the dielectric constant is related to the dynamic freezing of dipolar domains on the time-scale of simulations.

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Section: Dynamic Crossoversupporting

confidence: 64%

“…We therefore can conclude that the low-temperature phase is a disordered liquid. The orientational order can be detected by orientational order parameters typically defined for liquid crystals [55]. The order parameter p n is the average nth order Legendre polynomial P n (ê ·n)…”

Section: Dynamic Crossovermentioning

confidence: 99%

Dynamical and orientational structural crossovers in low-temperature glycerol

2016

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“…!.+(En -€ 1 )(n®n-t · .!) (5) where en , c 1 are the dielectric constants for parallel and perpendicular orientation of the director relative to the electric field.…”

Section: A Materials Functionsmentioning

confidence: 99%

Influence of surface anchoring and viscosity upon the switching behavior of twisted nematic cells

Stelzer

Hirning

Trebin

1993

Journal of Applied Physics

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Numerical calculations are presented on the dynamics of twisted chiral nematic cells. We are emphasizing the influence of surface effects on the optical switching behavior. Apart from the anchoring strength we have taken into account viscous effects at the surface by constructing a surface dissipation function. The dynamical light transmission curve has been determined for different strengths of the surface anchoring and various viscosity parameters by computer simulation.

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“…[1][2][3][4] A particularly interesting aspect is the possibility of preparing thermotropic MC-LCP with controlled molecular organization and orientational order 2 by polymerization of liquid crystal (LC) monomers started in a suitably ordered phase. Although this has been observed experimentally, [5][6][7] very little has been done on the modelling side to understand how the anisotropic medium can influence the features of the chains formed through the polymerization process.…”

Section: Introductionmentioning

confidence: 99%

A computer simulation study of the influence of a liquid crystal medium on polymerization

Berardi¹,

Micheletti²,

Muccioli³

et al. 2004

The Journal of Chemical Physics

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We present a simple molecular level model based on Gay-Berne monomers linked by Finitely Extendable Nonlinear Elastic Potential (FENE) bonds for describing main chain polymerization in liquid crystals. We apply the model to study the in uence that the order of the medium has on the characteristics of the chains obtained. We find that the chains prepared from the nematic are actually straighter than those obtained from a polymerization in the isotropic phase and that they are characterized by a small number of hairpins as experimentally observed.

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Thermotropic Liquid Crystals, Fundamentals

Cited by 575 publications

References 104 publications

Dynamical and orientational structural crossovers in low-temperature glycerol

Dynamical and orientational structural crossovers in low-temperature glycerol

Influence of surface anchoring and viscosity upon the switching behavior of twisted nematic cells

A computer simulation study of the influence of a liquid crystal medium on polymerization

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