The present invention is a composition comprising a stable aqueous dispersion of polymer particles comprising structural units of a nonionic monoethylenically unsaturated monomer; 2-(methacryloyloxy)ethyl phosphonic acid (MEP) or a salt thereof; and a sulfur acid monomer or carboxylic acid monomer or a combination thereof or a salt thereof, as well as a composite comprising the polymer particles adsorbed to the surface of a pigment particle such as TiO2. The composition and composite are prepared using the phosphorus acid monomer MEP, which can be prepared in high purity with low residual non-polymerizable phosphorus acid, thereby reducing the load of neutralizing agent required to achieve the targeted pH as compared with phophoethyl methacrylate (PEM).
