?
Nonlinear fluctuation effects in dynamics of freely suspended films
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics. 2015. Vol. 91. P. 032415-1–032415-8.
Kats E. I., V.V.Lebedev
Long-scale dynamic fluctuation phenomena in freely suspended films is analyzed. We consider isotropic films that, say, can be pulled from bulk smectic-
A liquid crystals. The key feature of such objects is possibility of bending deformations of the film. The bending (also known as flexular) mode turns out to be anomalously weakly attenuated. In the harmonic approximation there is no viscous-like damping of the bending mode, proportional to q 2 ( q is the wave vector of the mode), since it is forbidden by the rotational symmetry. Therefore, the bending mode is strongly affected by nonlinear dynamic fluctuation effects. We calculate the dominant fluctuation contributions to the damping of the bending mode due to its coupling to the inplane viscous mode, which restores the viscous-like q 2 damping of the bending mode. Our calculations are performed in the framework of the perturbation theory where the coupling of the modes is assumed to be small, then the bending mode damping is relatively weak. We discuss our results in the context of existing experiments and numeric simulations of the freely suspended films and propose possible experimental observations of our predictions.Keywords: liquid crystals
Захаров А. В., Düven H., Capar M. I., Physics Letters A 2026 No. 576 Article 131388
Molecular dynamics simulations were carried out to study the structural properties of nematic pentyl
cyanobiphenyl (5CB) and pentyloxy cyanobiphenyl (5OCB) liquid crystals (LCs) doped with gold nanoparti
cles (GNPs) of different numbers, shapes and sizes. The spherical GNPs of two different radii and rod-like have
been doped in 5CB and 5OCB cyanobiphenyl liquid crystals. In order to describe ...
Added: September 17, 2026
S̀liwa I., Maslennikov P., Pasechnik S. et al., Chemical Physics Letters 2025 Vol. 883 Article 142528
A numerical study of the effect of thermomechanical force on dissipation processes in a microsized compressible and incompressible hybrid aligned nematics has been carried out. Calculations have shown that under the effect of a temperature gradient , a hybrid aligned compressible and incompressible nematic samples settles down to the stationary flow regimes, and the thermomechanical force strongly ...
Added: November 27, 2025
Kasapenko N., Orlova T., N. Kondratyuk, Journal of Chemical Physics 2025 Vol. 162 No. 15 Article 154901
Molecular dynamics methods have proven their applicability for the simulation of the structure and properties of liquid crystals. For the reproduction of phase transitions in liquid crystals, many authors have reparameterized the classical force fields. For the first time, we demonstrate that even a general-purpose force field, for example, General AMBER Force Field (GAFF), without ...
Added: August 12, 2025
Romanov M., Yulia O. Koroleva, Journal of Non-Newtonian Fluid Mechanics 2023 Vol. 320 Article 105112
We have studied the two-dimensional axisymmetric Ericksen–Leslie equations with the non-zero inertial constant. The existence and uniqueness of the global weak solution is proved under certain assumptions. In the neighbourhood of the solid surface we derived the boundary layer equations and show that the effective viscosity of the liquid in the boundary layer decreases as ...
Added: January 4, 2024
P. V. Dolganov, K. D. Baklanova, Dolganov V. K., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2022 Vol. 106 No. 1 Article 014703
Focal conic structure formed near the transition from the cholesteric liquid crystal phase into isotropic liquid is studied in planar cells with a combination of optical methods. Employing a procedure with slow variation of temperature, we manage to obtain regions of periodic focal conic structure with two-dimensional square ordering in the plane of the cell. ...
Added: July 14, 2022
P.V. Dolganov, Зверев А. С., K. D. Baklanova et al., Soft Matter 2022 Vol. 18 P. 126–136
We investigated the coalescence of nematic droplets in an isotropic environment and that of isotropic droplets in a nematic environment in quasi-two-dimensional geometry of a flat optical cell. Two different regimes of coalescence were found. In the circular meniscus between the nematic and isotropic regions both nematic and isotropic phases exist. As a result, two bridges form at ...
Added: December 23, 2021
P.V. Dolganov, Zverev A. S., K.D. Baklanova et al., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2021 Vol. 104 No. 1 Article 014702
We observed the formation of small satellite droplets from the bridge at
droplet coalescence. Investigations were made using a Hele-Shaw cell in
the two-phase region at the nematic-isotropic phase transition. In
previous works on coalescence it was considered that before the start of
coalescence there exists a bridge between the outer fluid connecting
regions on the two sides of the ...
Added: October 4, 2021
Shuravin N. S., P.V. Dolganov, Dolganov V. K., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2018 Vol. 98 P. 052705-1–052705-6
Optical investigations and calculation of structures were performed on films of liquid crystal with the sequence of phase transitions in the bulk sample SmC*A − SmC*d3 − SmC*d4 − SmC* − SmC*α − SmA − I . We investigated freestanding nanofilms with number of smectic layers from 2 to 6 with thickness commensurate, smaller, or ...
Added: November 25, 2019
P.V. Dolganov, Cluzeau P., Dolganov V. K., Liquid Crystals Reviews 2019 Vol. 7 No. 1 P. 1–29
In this article we review interactions and collective behavior of inclusions in free-standing smectic films with in-plane orientational ordering. The inclusions interact on large distances and can form various self-organised structures. Topological defects of the director field play a key role in self-organization. Various types of interaction are realized, including dipolar, quadrupolar and interactions of ...
Added: November 21, 2019
Pavel V. Dolganov, Kats E., Dolganov V. et al., Soft Matter 2018 Vol. 14 P. 7174–7179
In this paper we report on observations of unusual linear defects forming spontaneously in polar freestanding smectic-C* films near the temperatures of thinning transitions. At high temperature a periodic structure of defects becomes the ground state of the system. We found that the defects are characterized by continuous rotation of the molecular orientation with a ...
Added: November 21, 2019
Shuravin N. S., P.V. Dolganov, Dolganov V. K., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2019 Vol. 99 No. 6 P. 062702
Freestanding smectic films give a unique possibility to study two-dimensional coalescence. We report experimental investigations in freestanding films and detailed analysis of coalescence of islands, circular regions of larger thickness than the surrounding film. The driving force of island coalescence is the dislocation tension on the boundary between the island and the film. The obtained ...
Added: November 21, 2019
P.V. Dolganov, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2018 Vol. 98 No. 3 P. 032707-1–032707-6
A large number of smectic phases can have the same energy when short-range interlayer interactions (interaction of nearest layers and frustrating next-nearest layer interaction) are taken into account. In this situation even weak long-range interactions become important. They lift the degeneracy and lead to the appearance of a manifold of polar structures with multilayer periodicity. ...
Added: November 21, 2019
P.V. Dolganov, Shuravin N. S., Dolganov V. K. et al., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2017 Vol. 95 No. 1 P. 012711
We report imaging of the director field near edge dislocations in thermotropic antiferroelecric smectic-C*A (SmC*A) liquid crystal. Measurements were made in freestanding films with thickness from two to ten smectic layers. We find two different orientations of the molecular tilt plane with respect to the edge dislocation line. The orientation is determined by the value ...
Added: November 21, 2019
V.V.Lebedev, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2019 Vol. 100 No. 2 P. 022705
We explain theoretical peculiarities of the smectic-A–hexatic-B equilibrium phase coexistence in a finite-temperature range recently observed experimentally in free-standing smectic films [I. A. Zaluzhnyy et al., Phys. Rev. E 98, 052703 (2018)]. We quantitatively describe this unexpected phenomenon within Landau phase transitions theory assuming that the film state is close to a tricritical point. We ...
Added: November 20, 2019
Vladimir V. Lebedev, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2018 Vol. 98 No. 5 P. 1–8
Experimental and theoretical studies of a smectic-A–hexatic-B transition in freely suspended films of thickness 2–10μm of the n-pentyl-4′−n-pentanoyloxy-biphenyl-4-carboxylate (54COOBC) compound are presented. X-ray investigations revealed a discontinuous first-order transition into the hexatic phase. The temperature region of two-phase coexistence near the phase transition point diminishes with decreasing film thickness. The width of this temperature region ...
Added: November 19, 2018
Yablonskii S. V., Kurbatov N. M., Parfenyev V.M., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2017 Vol. 95 No. 1 P. 012707-1–012707-5
We study horizontal streaming excited by means of a low-frequency and low-intensity acoustic wave in 2D freely suspended films of thermotropic smectic liquid crystals. Acoustic pressure induces fast periodic transverse oscillations of the film, which produce in-plane stationary couples of vortices slowly rotating in opposite directions owing to hydrodynamic nonlinearity. The parameters of the vortices ...
Added: October 30, 2017