Aqueous polymer dispersions which are obtainable by emulsion polymerization of ethylenically unsaturated monomers in an aqueous medium in the presence of free radical polymerization initiators and stabilizers, amphiphilic polymers which comprise one or more hydrophobic units (A) and one or more hydrophilic units (B) being used as the stabilizer before, during or after the polymerization, and the hydrophobic units (A) being formed from a polyisobutene block, at least 50 mol % of whose polyisobutene macromolecules have terminally arranged doubled bonds, processes for the preparation of the aqueous polymer dispersions by polymerizing ethylenically unsaturated monomers in the presence of free radical initiators and said amphiphilic polymers, which are used before, during or after the polymerization, and the use of the resulting aqueous polymer dispersions as associative thickeners in paper coating slips, in textile production, as thickeners for textile print pastes, in the pharmaceutical and cosmetics sector, for surface coatings, for detergents and cleaning agents, in foods and as oil field chemicals.