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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
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, Shuravin N. S., Dolganov V. K. et al., Soft Matter 2020 Vol. 16 No. 36 P. 8506-8511
In free-standing smectic films islands (regions of larger thickness than the film) can be considered as two-dimensional analogues of liquid droplets in a three-dimensional medium. The dynamics of droplet coalescence is an important but up to now incompletely solved problem in non-equilibrium mechanics. Here, we report on our investigations of island coalescence with the film meniscus. This phenomenon ...
Added: October 20, 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
Kats E. I., Muratov A. R., V.V.Lebedev, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2016 Vol. 93 P. 062707-1-062707-7
We propose a theoretical explanation for the long-standing problem of the anomalous critical behavior of the heat capacity near the smectic-A–hexatic phase transition. Experiments find a large specific heat critical exponent α=0.5–0.7, which is inconsistent with a small negative value α≈−0.01 expected for the three-dimensional XY universality class. We show that most of the observed ...
Added: October 27, 2016
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
P.V. Dolganov, Spiridenko N. A., Liquid Crystals 2022
In our work, we for the first time observed simultaneous birth and subsequent annihilation of two types of defects on nematic–isotropic interface: point boojums and localised equatorial defects. The investigations were made in the two-phase nematic–isotropic region in nematic droplets with conical boundary conditions. We found a new type of localized defects formed from equatorial ring defects in confined ...
Added: October 20, 2022
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
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
Долганов П. В., Долганов В. К., Кац Е. И., Письма в Журнал экспериментальной и теоретической физики 2022 Т. 115 С. 236-240
Обнаружен новый механизм утоньшения смектических нанопленок, отличающийся от ранее описанного в экспериментальных и теоретических работах. При температуре выше объемного фазового перехода Смектик-A - изотропная жидкость происходит изменение размера и формы мениска. Вблизи температуры неустойчивости нанопленок граница мениска углубляется в нанопленку, а толщина мениска становится порядка и меньше толщины нанопленки. Участок пленки меньшей толщины, который образуется в мениске у границы с пленкой, ...
Added: October 20, 2022
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
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
P.V. Dolganov, Shuravin N. S., Dolganov V. K., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2020 Vol. 101 Article 052701
We investigate in free-standing smectic films coalescence of holes (circular regions with thickness smaller than the surrounding film). This process can be considered as a two-dimensional analog of coalescence of bubbles in a three-dimensional fluid. A high speed video camera was used to study the evolution of domains at different stages of coalescence. Special attention was given to ...
Added: October 20, 2022
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
E.S. Pikina, M.A. Shishkin, Kolegov K. S. et al., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2022 Vol. 106 No. 5 P. 055105-1-055105-28
We present theoretical study and numerical simulation of Marangoni convection within ellipsoidal isotropic droplets embedded in free standing smectic films (FSSF). The thermocapillary flows are analyzed for both isotropic droplets spontaneously formed in FSSF overheated above the bulk smectic-isotropic transition and oil lenses deposited on the surface of the smectic film. The realistic model ...
Added: October 28, 2022
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
Бакланова К. Д., Долганов П. В., Долганов В. К., Journal of Surface Investigation: X-Ray, Synchrotron and Neutron Techniques 2021 Vol. 15 No. 4 P. 829-832
The transmission, reflection, and luminescence spectra of two types of samples of a cholesteric photonic crystal are measured: with the orientation of the n director specified by the surface of the optical cell, and when the n director is disoriented on the cell surface. In samples with surface orientation, a perfect helical structure is formed ...
Added: September 1, 2021
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
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
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
P.V. Dolganov, Shuravin N. S., Dolganov V. K. et al., Scientific Reports 2021 Vol. 11 Article 19144
We describe the collective behavior of isotropic droplets dispersed over a spherical smectic bubble, observed under microgravity conditions on the International Space Station (ISS). We find that droplets can form two-dimensional hexagonal structures changing with time. Our analysis indicates the possibility of spatial and temporal periodicity of such structures of droplets. Quantitative analysis of the hexagonal structure including the ...
Added: October 20, 2022
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