Distributions of Latex Particles Deposited from Water Suspensions

Abstract

AbstractWe used the atomic force microscope to determine the distributions of 150–200 nm diameter styrene-butadiene (SB) latex spheres with TR. = 45 °C deposited at sub monolayer coverages from water suspensions onto mica, glass, calcite and cellophane surfaces. Two deposition methods are used: drying of μl drops and dipping. For drop drying, the distributions are extremely inhomogeneous. A high density ring forms at the boundary of the area wet by the drop. At low suspension densities on cellophane, the ring is a close-packed monolayer several micrometers wide. Thicker rings form on calcite and glass. Inside the rings, the particle density is very low and non uniform; e.g., monolayer thick islands form on mica, short chains are predominant on calcite, small clusters form on glass, and isolated spheres occur on cellophane. Particle densities are substantially reduced near some substrate defects but are enhanced near others. For the dipping method, homogeneous distributions are obtained on glass and cellophane. The density of adsorbed particles increases linearly with immersion time and the distribution of monomers, dimers, and trimers is not characteristic of random adsorption.