Corona patterns around inclusions in freely suspended smectic films

Abstract

We discuss the structure and physical origin of corona patterns observed around solid or liquid spherical inclusions in freely suspended smectic films. Such patterns are observed when droplets or solid beads of micrometer size are sprayed onto the films. They are found in the smectic C phase and in the smectic A phase above such a smectic C phase, but disappear, for example, at the transition into a lower-temperature smectic B phase. We show that these structures are equivalent to splay domains found in the meniscus of freely suspended films, originating from surface-induced spontaneous splay.

A Gallery of Meniscus Patterns of Free-Standing Smectic Films

“…Similar stripe patterns have also been observed around inclusions of sufficiently large size in smectic C (smC) and smectic A (smA) phases [12][13][14]. Meyer and Pershan interpreted the stripes as the consequence of a spontaneous surface polarisation leading to c-director splay at the surfaces ("surface-splay domains") [2].…”

“…This conjecture has been confirmed numerically [18]. This result is in contrast to the more or less universal relation between stripe period and local meniscus thickness that is found experimentally [13].…”

“…The pattern behaviour on heating from the smC to the smA phase has been described in Refs. [13,16]: Stripes disappear/reappear during heating/cooling at some material-specific temperature above the smC-smA transition in the homogeneous parts of the FSF. During heating, the stripe period remains nearly constant, while the stripe contrast diminishes continuously.…”

“…Stripe patterns are found if and only if the material possesses a smC phase, no matter whether this phase is chiral or not [13]. The basic features of the textures in different materials are identical, while details may vary when the patterns are observed under crossed polarisers.…”

Plateau borders of smectic liquid crystalline films

“…Moreover, such a large contact angle would be detectable in the catenoid profiles. In smectic C films, contact angles of the order of ≈ 5 • have been measured [31], and the influence of such contact angles on line tensions of Plateau borders should in principle be detectable, when smectic A and C films are compared.…”