1,720,967 research outputs found
Controlling surface defect valence in colloids
No full textWe perform large-scale Monte Carlo simulations of orientational ordering in nematic shells and study the type and position of topological defects when an external electric field (homogeneous or quadrupolar) is applied. The field-induced variation of the defect number (and strength) can be used to change the valence of colloidal particles coated with a nematic layer
Molecular simulations elucidate electric field actuation in swollen liquid crystal elastomers
No full textSwollen elastomer liquid crystals undergo significant deformations
by application of an electric field perpendicular to their alignment
axis, as shown in experiments by Urayama et al. [Urayama K,
Honda S, Takigawa T (2006) Macromolecules 39:1943–1949]. Here
we clarify this surprising effect at the molecular level using largescale
Monte Carlo simulations of an off-lattice model based on a
soft Gay–Berne potential. We provide the internal change of molecular
organization, as well as the key observables during the
actuation cycle
Biaxial liquid crystal elastomers: a lattice model
No full textWe present a simple coarse-grained lattice model for monodomain biaxial liquid-crystal elastomers and perform large-scale Monte Carlo simulations in the proposed model system. Orientational ordering —uniaxial or biaxial— reflects in sample deformations on cooling the system. The simulation output is used to predict calorimetry data and deuterium magnetic resonance spectra
Defects and ordering in nematic coatings on uniaxial and biaxial colloids
No full textWe present a systematic lattice Monte Carlo simulation study of nematic ordering in thin nematic shells on uniaxial and biaxial colloidal particles. Typically, four mutually repulsive half-strength defect
lines penetrating the shell are observed, as found for spherical particles. For shells of constant thickness, the defect lines tend to accumulate in the high curvature regions. If the thickness of the
nematic coating varies across the surface, the defect lines tend to be located in the thinnest regions. On increasing the shell thickness, the defect lines transform into escaped structures with surface point
defects
Main-chain swollen liquid crystal elastomers: A molecular simulation study
No full textWe have performed large-scale off-lattice computer simulations in a model system of swollen mainchain liquid-crystalline elastomers, constituted of weakly reticulated soft Gay–Berne chains,
investigating both nematic and smectic morphologies. We present isostress Monte Carlo results for temperature-scan and stress–strain experiments, and connect to typical experimental observables, such
as sample dimensions, specific heat, deuterium magnetic resonance spectra, and scattered X-ray patterns. We find that the results reproduce the main features of main-chain elastomers, e.g.,
a pronounced strain-alignment coupling and the existence of two (nematic–isotropic and smectic–nematic) order–disorder phase transitions. The nematic–isotropic transition in our system turns out to
be weakly first-order
External field-induced switching in nematic elastomers: a Monte Carlo study
No full textWe present a Monte Carlo study of external field-induced switching in nematic elastomers, employing a coarse-grained shearable lattice model. In large enough systems a full-wavelength Freedericksz effect is observed as opposed to the half-wavelength effect seen in ordinary nematics that clearly reflects in simulated polarized light textures, as well as in deuterium magnetic resonance spectra. The reorientation of mesogenic units is accompanied by pronounced shear deformations
A microscopic lattice model for liquid crystal elastomers
No full textWe propose a simple coarse-grained lattice model for liquid crystal elastomers and show, through large scale Monte Carlo simulations,
that it can reproduce stress–strain, order, light transmission, and other experiments, including temperature effects. We
focus both on homogeneously and inhomogeneously crosslinked materials
Computer simulations of liquid crystal polymeric networks and elastomers
No full textA review of computer simulations of liquid crystal elastomers, describing mainly lattice tmodel
Lattice spin models of polymer-dispersed liquid crystals
No full textMonte Carlo simulations of lattice spin models are a powerful method for the investigation of confined nematic liquid crystals and allow for a study of the molecular organization and thermodynamics of these systems.
Investigations of models of polymer-dispersed liquid crystals are
reviewed devoting particular attention to the calculation of deuterium NMR spectra from the simulation data
The effect of varying surface orientation on the molecular organization of nematic films. A Monte Carlo simulation
No full textWe present a Monte Carlo (MC) simulation of a nematic film with boundary conditions that vary from a homogeneous to a homeotropic anchoring at one surface while having a homogeneous anchoring at the other one. The simulations are based on the Lebwohl-Lasher lattice spin model with suitable boundary conditions to mimic the cell. We have investigated temperature effects on the molecular organisation inside the system by calculating the internal energy, the heat capacity and the standard nematic order parameter
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