Anisotropy of the Line Tension and Bulk Elasticity in Two-Dimensional Drops of a Mesophase

Abstract

Using Brewster angle microscopy to study Langmuir monolayers of fatty acids at the air-water interface, we have observed a boojum pattern in two-dimensional drops of a tilted liquid condensed phase. In a boojum, the in-plane molecular orientation turns continuously and points with the same molecular orientation are located on straight lines, crossing at a defect point expelled from the drop. We have observed a distortion of the drops in the neighborhood of these points. We have studied the distortion of the drops and the distance of the defect point to the drop boundary, and deduced several ratios between elastic constants, anisotropic line tension, and elastic constants of the medium.