Structure in a Confined Smectic Liquid Crystal with Competing Surface and Sample Elasticities

We report on studies using the x-ray surface forces apparatus (XSFA) to compare the structure of a liquid crystal confined between hard surfaces and, for the first time, between soft surfaces that can deform due to the stresses imposed by the confined fluid. We find that the alignment of smectic domains in confined films depends critically on both the shape and compliance of the confining walls or surfaces: ``Soft surfaces'' exhibit a critical gap thickness of 3.4 {μ}m for the liquid crystal studied at which maximum alignment occurs, while ``hard surfaces'' do not exhibit gap-dependent alignment.