Control of charge densities for cationic latex particle

We report a systematic investigation, together with a new method, on controlling cationic charge densities of latex particles. A covalently bonded charge density up to 100 equiv/g was achieved on the basis of copolymers of glycidyl methacrylate (GMA) and butyl methacrylate (BMA) by either surfactant-free or nonionically stabilized emulsion polymerization, followed by the aminolysis of epoxy groups into quaternary ammonium groups. The cationic charge density was successfully controlled by adjusting the ratio between epoxy and amino groups. It was found that the formation of disadvantageous water-soluble polyelectrolytes was negligible. Cationic charges were also introduced to latex particles by using cationic azo initiators and/or copolymerization with cationic or amine-containing comonomers, but colloidal titrations showed that controlled formation of highly charged cationic latex particles without the formation of water-soluble polyelectrolytes was only achievable for the aminolysis approach.