PHASE-DIAGRAM AND MORPHOLOGY OF ANISOTROPIC DOMAINS IN A PURE AND MIXED CARBOCYANINE MONOLAYER

A film of amphiphilic carbocyanine dye is spread on water and observed by fluorescence and polarized light techniques. With ClO4- counterion s in the subphase, a first order transition occurs between an isotropi c liquid phase and a solid one, made of birefringent elongated domains . On pure or acidified water, this transition takes place at a higher surface pressure, close to the monolayer collapse. When the carbocyani ne is mixed with a fraction x of stearic acid another condensed phase appears, made of birefringent disks growing around a central disinclin ation. We report data concerning the phase diagram, and present a phot ometric method to measure the film thickness. We also discuss the natu re of the different phases, and the possibility of a smectic-to-isotro pic transition at x = 0.6.