Relation between static short-range order and dynamic heterogeneities in a nanoconfined liquid crystal

Lefort, Ronan; Morineau, Denis; Guégan, Régis; Guendouz, Mohammed; Zanotti, Jean-Marc; Frick, B.

doi:10.1103/physreve.78.040701

Cited by 34 publications

(28 citation statements)

References 31 publications

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“…[24,44,71,72] Albeit the simulation studies indicate a rather smooth transition in the molecular mobility [44,71,72] between the interface region and the core, whereas according to our experiments this transition is quite sharp, resulting in a very distinct monolayer and core behaviour. Moreover, our filling-fraction dependent experiments provide information on the thermotropic orientational order as a function of mesoscopic arrangement of the nematic liquid in the channels (capillary-and film-condensed states).…”

Section: Discussionmentioning

confidence: 49%

“…However, the detailed partitioning, the evolution of the relaxation behaviour and the superposition of the distinct relaxation contributions of LCs as a function of the filling of nanoporous media has been elusive so far and also controversially discussed [44,71,72]. Here we employ dielectric relaxation spectroscopy on an archetypical rod-like liquid crystal (7 CB) confined in an array of isolated channels of approximately 7 nm radius in a monolithic silica membrane.…”

Section: Fig 1: (Color Online)mentioning

confidence: 99%

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Inhomogeneous relaxation dynamics and phase behaviour of a liquid crystal confined in a nanoporous solid

et al. 2015

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We report filling-fraction dependent dielectric spectroscopy measurements on the relaxation dynamics of the rod-like nematogen 7CB condensed in 13 nm silica nanochannels. In the film-condensed regime, a slow interface relaxation dominates the dielectric spectra, whereas from the capillarycondensed state up to complete filling an additional, fast relaxation in the core of the channels is found. The temperature-dependence of the static capacitance, representative of the averaged, collective molecular orientational ordering, indicates a continuous, paranematic-to-nematic (P-N) transition, in contrast to the discontinuous bulk behaviour. It is well described by a Landau-deGennes free energy model for a phase transition in cylindrical confinement. The large tensile pressure of 10 MPa in the capillary-condensed state, resulting from the Young-Laplace pressure at highly curved liquid menisci, quantitatively accounts for a downward-shift of the P-N transition and an increased molecular mobility in comparison to the unstretched liquid state of the complete filling. The strengths of the slow and fast relaxations provide local information on the orientational order: The thermotropic behaviour in the core region is bulk-like, i.e. it is characterized by an abrupt onset of the nematic order at the P-N transition. By contrast, the interface ordering exhibits a continuous evolution at the P-N transition. Thus, the phase behaviour of the entirely filled liquid crystal-silica nanocomposite can be quantitatively described by a linear superposition of these distinct nematic order contributions.

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Section: Discussionmentioning

confidence: 49%

Section: Fig 1: (Color Online)mentioning

confidence: 99%

Inhomogeneous relaxation dynamics and phase behaviour of a liquid crystal confined in a nanoporous solid

et al. 2015

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“…Concerning dynamics, some striking similarities between confined LCs and glass-forming systems are reported in many studies, such as a non-Debye character of the relaxation decay and a non-Arrhenius temperature dependence of the relaxation time [33][34][35]. Elastic fixed window neutron backscattering experiments on 8CB confined in silicon nanochannels are shown in Fig.…”

Section: Dynamics Of Nanoconfined Liquid-crystalsmentioning

confidence: 99%

“…A model taking this heterogeneity into account and based on simple hypothesis has been used by Lefort et al [33]. It assumes that i) the surface dynamics is frozen within the experimental resolution (r = R), ii) far from the surface, the dynamics tends to that of the bulk, following a simple exponential decay 1 (r) ∝ exp( R−r wall ) where 1 (r) is the inverse local relaxation time at a distance r from the pore center, R is the pore radius, and wall is the dynamical correlation length that characterizes the range of influence of the surface on the molecular dynamics and iii) the relaxation modes remain qualitatively the same as in the bulk.…”

Section: Dynamics Of Nanoconfined Liquid-crystalsmentioning

confidence: 99%

Physics of fluids confined in nanochannels: A shared space for neutrons and simulation

Morineau¹

2011

Journées de la Neutronique

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Abstract. Manipulating fluids at the nanoscale by geometrical confinement is a major issue of contemporary condensed matter science. It is also an area of research where the complementarity of neutron scattering and molecular simulation is particularly apparent. In the present contribution, we consider different cases from the recent literature, where structural (diffraction) and dynamical (quasielastic scattering) investigations by neutron methods can benefit from realistic (atomistic) and coarse-grained molecular simulations, and viceversa. We will emphasize the special benefits and the limitations of each type of approach with the ultimate hope to inspire more scientists to bridge the gap between experiments and simulation.

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“…Liquid crystals represent a state of order intermediate between truly crystalline and truly liquid. Many different types exist involving varying degrees of short and long-range translational and orientational order (Brasselet & Galstian, 2000;Gué gan et al, 2006;Lefort et al, 2008;Chahine et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Diffuse scattering and partial disorder in complex structures

Welberry

Goossens

2014

Int Union Crystallogr J

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The study of single-crystal diffuse scattering (SCDS) goes back almost to the beginnings of X-ray crystallography. Because SCDS arises from two-body correlations, it contains information about local (short-range) ordering in the sample, information which is often crucial in the attempt to relate structure to function. This review discusses the state of the field, including detectors and data collection and the modelling of SCDS using Monte Carlo and ab initio techniques. High-quality, three-dimensional volumes of SCDS data can now be collected at synchrotron light sources, allowing ever more detailed and quantitative analyses to be undertaken, and opening the way to approaches such as three-dimensional pair distribution function studies (3D-PDF) and automated refinement of a disorder model, powerful techniques that require large volumes of low-noise data.

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Relation between static short-range order and dynamic heterogeneities in a nanoconfined liquid crystal

Cited by 34 publications

References 31 publications

Inhomogeneous relaxation dynamics and phase behaviour of a liquid crystal confined in a nanoporous solid

Inhomogeneous relaxation dynamics and phase behaviour of a liquid crystal confined in a nanoporous solid

Physics of fluids confined in nanochannels: A shared space for neutrons and simulation

Diffuse scattering and partial disorder in complex structures

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