Observation of first order phase transitions in monolayers without fluorescent probes
Abstract
We have built a microscope employing the characteristics of reflection at the Brewster angle, in order to observe coexisting domains of different phases in monolayers without adding fluorescent probes. This microscope is sensitive to variations of the density and anisotropy in the film. We have used this new technique to study the formation of a monolayer at the free surface of solutions of a soluble amphiphile, sodium octanoate. The formation of the film is very slow, which can be explained by the existence of a surface potential barrier which the molecule must cross before reaching the surface. The growth of the monolayer can be divided into four stages.