A method for modifying the properties of a suspension of solid or liquid particles in an aqueous medium, includes the step of adding to the suspension or to the aqueous medium a polymer prepared by inverse emulsion polymerization of monomers Ab, comprising a betaine group, and of nonionic monomers Ba included in an aqueous phase dispersed in the form of droplets in a hydrophobic external phase, wherein the molar ratio of the monomers Ab to the monomers Ba is from about 4/96 to about 40/60, the polymer exhibits an intrinsic viscosity of greater than 600 mL/g, the reduced specific viscosity being measured by dissolving the polymer in a 20% by weight aqueous NaCl solution.