Optical Analysis of the Surface Smectic O Film

Birefringence measurements are performed at normal and oblique incidence on the smectic O films induced at the free surface of isotropic puddles of 1-(methyl)-heptyl-terephthalidene-bis-amino cinnamate (MHTAC). The analysis of these measurements, together with the measurements of the electric polarizations in the chiral compound, shows that the last layer of the film, in contact to the isotropic phase, is indeed nematic and thicker (≃ 7 nm) than the other layers (3 nm), and suggests that the tilt angles in the first and last layers are smaller than in the bulk layers of the film.