Shear-induced optical anisotropy in a Langmuir monolayer: a Brewster angle reflectivity study

Under shear, some specific films present an in-plane molecular alignment. Assuming that the optical property of a such monolayer is similar to that of a 2D nematic liquid crystal, we demonstrated that shearing the initially isotropic film by a rotating disk can lead to an optical anisotropy at the interface. Theoretically, the Brewster angle microscopy image of the monolayer appears like a distorted extinction cross. Experimentally, reflectivity measurements on a mesogenic polyacrylate monolayer fit well the model and shows for the first time shear induced optical anisotropy.