Nonionic latices in aqueous media part 1. Preparation and characterization of polystyrene latices

Abstract

A series of non-ionic polystyrene latices in aqueous media containing particles with a narrow size distribution have been prepared using a nonyl phenol poly(ehylene glycol) condensate as the surfactant, methoxy poly(ethylene glycol methacrylate) as the comonomer/stabilizer, and ascorbic acid/hydrogen peroxide as the initiator system. As a control synthesis for comparison with the above latex, a charge stabilized polystyrene latex was prepared, using an anionic surfactant and potassium persulphate as the initiator. Latices employing a combination of charge plus steric stabilization mechanisms were also prepared, in order to investigate the effect of the non-ionic surfactant and the comonomer/stabilizer. The particle size of the latices was measured by transmission electron microscopy, the surface charge density by conductimetric titration and the glass transition temperature of the polymer by differential scanning calorimetry. The latex prepared using non-ionic ingredients, showed no titratable charge and exhibited a profound lowering of the glass transition temperature, with respect to the charge stabilized latex. On the basis of these results, schematic models for the polymerization mechanism and the morphology of the latex particles are proposed.