MONOLAYER OF POLYSTYRENE MONOMOLECULAR PARTICLES ON A WATER-SURFACE STUDIED BY LANGMUIR-TYPE FILM BALANCE AND TRANSMISSION ELECTRON-MICROSCOPY

The behavior of a monolayer of polystyrene monomolecular particles which was obtained by spreading dilute solutions in benzene on the water surface was studied by a Langmuir-type film balance and transmission electron microscopy (TEM). Since polystyrene has no hydrophilic group, the surface pressure measured by the film balance was not due to the real decrease of the surface tension but due to a mechanical force by compression, thus the pi minus A curves were apparent pi minus A curves. However, the macroscopic observation by the film balance was in good agreement with the microscopic observation by TEM, indicating the particles are stable against the compression. At the limiting area, A//0, the monomolecular particles covered 56% of the water surface, but they could not be most closely packed by further compression. Apparent pi minus A curves were measured for lower molecular weight samples, for which formation of monomolecular particles has not been confirmed. The observed small A//0 indicated the particles were not formed or were unstable against the compression.