Self-organization of N* inclusions in SmC* free-standing films

Abstract

The behaviour of freely suspended smectic-C* ( SmC(*)) films at the bulk SmC(*)-cholesteric ( N(*)) phase transition has been investigated using polarized-reflected-light microscopy. Our experimental observations show that above the bulk SmC(*)- N(*) phase transition the N(*) order appears in different ways according to the film thickness. In thin films, the conventional layer-by-layer thinning occurs. In films of intermediate thickness N(*) inclusions nucleate inside the SmC(*) film. The distortions of the in-plane orientational order of the SmC(*) host phase induce elastic interactions between the inclusions and lead to their self-organization in chain-like structures. Both the dynamic of the chaining and the parameters driving the equilibrium distance between the inclusions in the chain are investigated. In thick films, N(*) fingers grow inside the film. The influence of the experimental conditions on the various processes is analysed.

Colloidal particles in liquid crystal films and at interfaces

“…Dispersions are normally prepared by using well-controlled cycles of heating/cooling of free standing smectic films [90]. In order to initiate the nucleation of the lower order inclusions, the smectic film is gradually heated across the corresponding bulk transition temperature until the temperature of nucleation is reached.…”

Inclusions in Smectic C Films as Modeled by Disclinations

“…Optical analysis of the texture has revealed a radial c-director anchoring at the surface separating S C * and N* phases and the presence of a (−1)-wedge disclination in the neighbourhood of the inclusion [1][2][3]. The N* droplet can be represented by a (+1)-wedge disclination of finite length equal to the droplet length in the direction perpendicular to smectic layers.…”

“…The (−1)-wedge disclination corresponds to the notion of hyperbolic defect discussed in the Refs. [1][2][3]. Segments of (±1)-disclinations cannot terminate in the bulk of the film, but they are connected to form a disclination loop.…”

“…The chain formation in these films was explained as the consequence of dipolar interaction of inclusions [1][2][3][4].…”

Direct Measurement of Interaction Forces Between Islands on Freely Suspended Smectic C Films Using Multiple Optical Tweezers

“…The structure and mechanical and thermodynamical properties of films have been widely studied since they were discovered by Friedel in 1922 [1,2]. Investigations of topological defects and the selforganization of circular inclusions in smectic C (SmC) free-standing films are quite recent [3][4][5][6][7][8]. Pettey et al [3] derived an expression for the director field associated with islands containing topological defects by minimizing the Frank elastic free energy of a smectic C film in 2D, assuming fixed boundary conditions on a circular disk on the film representing the island, and showed that there is a hyperbolic −1 point defect at a distance R 2 from the center where R is the disk radius.…”