Preparation and properties of polystyrene model colloids: I. Preparation of surface-active monomer and model colloids derived therefrom

Model colloids having known particle size and surface chemistry are highly desirable for use in a variety of studies, such as colloid stability, interactions between particles and walls, measurement of diffusion coefficients, and rheology. Independent control of particle size and surface functional group density cannot, however, be achieved by conventional emulsion polymerization methods. This article is concerned with a method by which this goal can be accomplished by means of a surface-active comonomer, sodium sulfodecylstyryl ether (SSDSE), which was synthesized through four-step sequences of reactions starting from coumarin. Several series of monodisperse polystyrene latexes of the same size have been prepared, covering a range of particle size with radius from 90 to 120 nm, polydispersity indices on the average of 1.005 to 1.015 and surface charge densities from ca. 1.0 to 10.0 μC/cm 2. These latexes were synthesized by a two-step process. First, monodisperse latexes with low surface charge density were formed by means of conventional emulsion polymerization. Then, a seed copolymerization with the surface-active comonomer was used to control the surface charge density of the latex.