The present invention relates to a polymer blend, comprising (a) at least one hydrophobic polymer, as component A, (b) at least one hydrophilic polymer, as component B, and (c) at least one structural unit that crosslinks component A and/or B and derives from at least one compound selected from the group consisting of aldehydes, dialdehydes, diketones, aldehyde ketones, derivatives of the abovementioned compounds, and mixtures thereof, as component C, and to processes for the production thereof and to the use thereof.