The present invention relates to a method for making a direct emulsion of a copolymer in water, characterized in that it comprises the polymerization of at least, expressed as a percentage by weight of each of the monomers based upon the total weight of the monomers: a) 10 to 80% by weight of methacrylic acid and, optionally, of acrylic acid； b)15 to 80% by weight of at least one non-ionic vinyl monomer； c) 0.05 to 9.5% by weight of 2-acrylamido-2-methylpropane sulfonic acid or a salt thereof； d) 0.5 to 30% by weight of at least one monomer containing at least one hydrophobic group； and e) 0.01 to 5% by weight of at least one crosslinking monomer； said polymerization being carried out in the presence of at least one surfactant. It also relates to the corresponding new copolymer emulsion in water, a method for thickening an aqueous composition comprising such an emulsion of copolymer and to an aqueous composition comprising such a copolymer emulsion.
