Structural, Optical and Dynamic Properties of Thin Smectic Films

Sublimation of isolated toric focal conic domains on micro-patterned surfaces

Toric focal conic domains (TFCDs) in smectic liquid crystals exhibit distinct topological characteristics, featuring torus-shaped molecular alignment patterns with rotational symmetry around a central core. TFCDs have attracted much interest due to their unique topological structures and properties, enabling not only fundamental studies but also potential applications in liquid crystal (LC)-based devices. Here, we investigated the precise spatial control of the arrangement of TFCDs using micropatterns and sublimation of TFCDs to estimate the energy states of the torus-like structures. Through simulations, we observed that the arrangement of TFCDs strongly depends on the shape of the topographies of underlying substrates. To accurately estimate the energetic effects of non-zero eccentricity and evaluate their thermodynamic stability, we propose a geometric model. Our findings provide valuable insights into the behavior of smectic LCs, offering opportunities for developing novel LC-based devices with precise control over their topological properties.

Flows Excited by Shear Stress in Freestanding Symmetric Smectic C Films

The purpose of this paper is to show some useful routes in describing the shear-driving flows in a freely suspended symmetric smectic C film stretched between two circular frames, the rest outer and rotating inner frames. Our calculations, based on a corresponding extension of the Eriksen–Leslie theory, show that the shear-driving flow in the film, excited by a rotating inner circular frame, causes a twisting rotation of the c^-director around the normal to smectic layers. It is found that the shear flow excited by the rotating frame in a positive sense (counterclockwise) causes a twisting rotation of the c^-director in a negative sense (clockwise) around the normal to smectic film. It is also shown that the twisting of the c^-director’s field has a jumping nature when a large reorientation is carried out in a short space of time. It was also shown that the twisting dynamics of the c^-director field strongly depends on the curvature of the inner rotating frame.

Nematic and Smectic Phases: Dynamics and Phase Transition

We study in this paper the dynamics of molecules leading to the formation of nematic and smectic phases using a mobile 6-state Potts spin model with Monte Carlo simulation. Each Potts state represents a molecular orientation. We show that, with the choice of an appropriate microscopic Hamiltonian describing the interaction between individual molecules modeled by 6-state Potts spins, we obtain the structure of the smectic phase by cooling the molecules from the isotropic phase to low temperatures: molecules are ordered in independent equidistant layers. The isotropic-smectic phase transition is found to have a first-order character. The nematic phase is also obtained with the choice of another microscopic Hamiltonian. The isotropic-nematic phase transition is a second-order one. The real-time dynamics of the molecules leading to the liquid-crystal ordering in each case is shown by a video.