Journal of Chemical Physics, Vol.101, No.9, 8258-8261, 1994
Domain Morphology in a 2-Dimensional Anisotropic Mesophase - Cusps and Boojum Textures in a Langmuir Monolayer
Brewster angle microscopy (BAM) and polarized fluorescence microscopy (PFM) were used to observe domains of a tilted condensed phase in coexistence with an isotropic liquid phase in Langmuir monolayers of pentadecanoic acid. The orientation of the molecular tilt direction inside the domains can be described as a "virtual boojum" texture and a cusp appears in the domain boundary at the vertex of the boojum. The angle subtended by the cusp increases with the domain size for domains greater than 25 mu m in diameter. All of these observations are at least qualitatively consistent with the recent predictions of a generalized Wulff construction for deformable materials [J. Rudnick and R. Bruinsma, Phys. Rev. Lett. (submitted)].
Keywords:BREWSTER-ANGLE MICROSCOPY;AIR-WATER-INTERFACE;PHASE-TRANSITIONS;FLUORESCENCE MICROSCOPY;VISUALIZATION;1ST-ORDER