Preparation of monodisperse polystyrene latices by Y-ray polymerization and their electron-microscopic and electrophoretic characterization

The preparation of monodisperse polystyrene latices by the initiation with y-rays from €•)Co is described. The latices were prepared by the direct polymerization method in the presence of the emulsifier Aerosol MA. The latex samples were characterized with regavd to the particle size, the particle size diskibution, and the ·surface particle charge by the methods of electron microscopy and moving boundary electrophoresis. The surface properties of latex particles were examined on samples exhaustively dialysed against distilled water and tTeated with ion-exchange resins. The results were compared with data collected on latices prepared by persulfate initiation. The latices prepared by y-ray initiated polymerization proved to have a somewhat smaller particle size and a higher degree of monodispersity in a wider range of the emulsifier concentration than those prepared by persulfate initiated polymerization. Whereas with persulfate initiation monodisperse latices were obtained at emulsifier concentrations near to the critical micelle concentration, with irradiation initiation monodisperse samples were formed at higher emulsifier concentrations. It was found that the mechanism of polymerization in the presence of Aerosol MA deviates from those formulated by Smith and Ewart. From data on electrophoretic mobility of particles the zeta-potentials and particle surface cha·rge densities for various prepared latices were calculated. On the basis of measurements of electrophoretic mobility in relation to pH values of latex suspensions the character of functional groups which contributed to the total particle surface charge is discussed