New surface elastic constant in asymmetric films of tilted molecules
Institut de Physique et Chimie des Matériaux de Strasbourg
23 rue du Lœss, 67037 Strasbourg, France
Corresponding author: Yves.Galerne@ipcms.u-strasbg.fr
Accepted: 25 May 2001
A 2-dimensional, linear-splay elastic constant K1 is evidenced in ultrathin prefreezing (and prewetting) films of a tilted smectic liquid crystal (MHTAC). Though small, , K1 may produce visible effects in quasi-2D systems. We show, in particular, that K1 is able to promote a purely elastic instability in the film, corresponding to a continuous rotation of the director. This instability is characterized by typical patterns of stripes with a 4-fringe periodicity between crossed polarizers, which denote variations of the molecular tilt angle in the splay regions. K1 should also exist in Langmuir and biological films as well.
PACS: 61.30.Gd – Orientational order of liquid crystals; electric and magnetic field effects on order / 64.70.Md – Transitions in liquid crystals / 68.08.-p – Liquid-solid interfaces
© EDP Sciences, 2001