arXiv subjects

P. V. Dolganov

Publications and source records attributed to P. V. Dolganov.

4 recordsLinked to original sources

arXiv2021

Dynamics of capillary coalescence and breakup: quasi-two-dimensional nematic and isotropic droplets

For the first time we observed 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 nematic-isotropic phase transition. In previous works on coalescence it was considered that before start of coalescence there exists a bridge between the outer fluid connecting regions on the two sides of the droplets (outer bridge). After start of coalescence a bridge connecting the two droplets appears (droplet bridge) and the outer bridge is broken. For the first time we have shown that there are coalescence processes when after start of coalescence both the droplet bridge and the outer bridge can exist. This cardinally changes the coalescence process. During the first coalescence stage the size of the outer bridge decreases, the size of the droplet bridge increases. During the second stage the outer bridge becomes unstable with pinch-off, formation of pointed end domains, secondary instability, splitting of pointed end domains and formation of satellite droplets. Our work connects two areas of fluid dynamics: coalescence and breakup with formation of satellite droplets.

cond-mat.soft↗

arXiv2010

Undulation instabilities in the meniscus of smectic membranes

Using optical microscopy, phase shifting interferometry and atomic force microscopy, we demonstrate the existence of undulated structures in the meniscus of ferroelectric smectic-C* films. The meniscus is characterized by a periodic undulation of the smectic-air interface, which manifests itself in a striped pattern. The instability disappears in the untilted smectic-A phase. The modulation amplitude and wavelength both depend on meniscus thickness. We study the temperature evolution of the structure and propose a simple model that accounts for the observed undulations.

cond-mat.soft↗

arXiv2010

Liquid-Crystal Smectic with Six-Layer Periodic Structure

Recently Wang et al. [Phys. Rev. Lett. 104, 027801 (2010)] discovered a new polar smectic phase with six-layer period (SmC*d6). In this manuscript, we demonstrate that the theory [Phys. Rev. E 67, 041716 (2003)] based on the free energy expansion with a two-component order parameter predicted the six-layer phase, describes its structure and the phase sequence observed in experiment [Phys. Rev. Lett. 104, 027801 (2010)].

cond-mat.soft↗

arXiv2005

Structures and orientational transitions in thin films of tilted hexatic smectics

We present detailed systematic studies of structural transformations in thin liquid crystal films with the smectic-C to hexatic phase transition. For the first time all possible structures reported in the literature are observed for one material (5 O.6) at the variation of temperature and thickness. In unusual modulated structures the equilibrium period of stripes is twice with respect to the domain size. We interpret these patterns in the frame work of phenomenological Landau type theory, as equilibrium phenomena produced by a natural geometric frustration in a system having spontaneous splay distortion.

cond-mat.soft↗