Mechanisms involved in the stabilization of latex particles by adsorbed block copolymers in emulsion polymerization process

The efficiency of amphiphilic block copolymers composed of butyl methacrylate and methacrylic acid (PBMA-b-MAA) of various compositions was evaluated in terms of colloidal stability. These copolymers were adsorbed on a PBMA latex in quantities inferred from adsorption isotherm and their colloidal stability was investigated through the determination of the critical coagulation concentration CCC, by addition of either electrolyte or acid. The latexes covered with block copolymers were very stable against addition of either electrolyte or acid compared to the bare latex. The colloidal stability as evaluated by the CCC, increased with the relative coverage. The results were discussed in relation with the behavior obtained in emulsion polymerization. The overall trends were sorted correctly since a better coverage yielded a better colloidal stability and a smaller size at the end of emulsion polymerization. But no direct correlation could be found out between adsorption, colloidal stability and emulsion polymerization. Influence of stirring during the flocculation test was also evaluated.