Abstract

We report an experimental investigation of the structure of periodic patterns observed in the meniscus of free-standing smectic films. Combination of polarizing optical microscopy and phase shifting interferometry enabled us to obtain new information on the structure of the meniscus, and in particular, on the topography of the smectic-air interface. We investigate the profile of the undulations in the striped structure in the thin part of the meniscus, change of the stripe period with the meniscus thickness and subsequent transition into a two-dimensional structure. It is shown that the two-dimensional structure has an unusual complex profile of "egg-box" type. The striped texture occurs upon cooling from the nontilted smectic-A to the smectic-C* phase, whereas the two-dimensional pattern is present in both phases. We discuss the possible origin of the modulated structures, the role of the dislocations in the meniscus, the elasticity of smectic layers, and the mechanical stress induced by dislocations.

Highlights

  • The meniscus in smectic films is of paramount importance in many aspects

  • We have reported a detailed experimental study of the structures that decorate the meniscus of free-standing smectic films

  • The structures only appear in areas where thickness gradients exist, including the wedge surrounding colloidal particles trapped in the film, and are absent in flat zones

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Summary

Introduction

The meniscus in smectic films is of paramount importance in many aspects. The meniscus free surface in SmC (SmC*) films exhibits nontrivial undulations, which manifest themselves optically in a quasi-periodic striped pattern parallel to the thickness gradient.[6,7,8,9] The patterns are long lived and remain as long as the smectic film is stable. These experiments clearly show that LC menisci can be rugged, in contrast to their isotropic counterparts. This is obviously a direct consequence of the elastic properties of smectics

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