The present invention provides polymer blends comprising the components (a) from 40% to 95% by weight of at least one polyaryl ether copolymer constructed of (a1) from 50% to 99.9% by weight of building units of the general formula I and from 0% to 40% by weight of further building units II selected from segments of one or more thermoplastic polymers, and (a2) from 0.1% to 10% by weight of at least one crosslinker V having at least three hydroxyl functionalities, the at least one crosslinker V being present in component (a) in converted form and the sum total of % by weight for (a1) and (a2) being 100% by weight, and (b) from 5% to 60% by weight of at least one hydrophilic polymer selected from polyvinylpyrrolidone, polyvinylpyrrolidone copolymers, polyethylene glycol, polypropylene glycol, copolymers of ethylene glycol and propylene glycol, water-soluble cellulose derivatives, polyamide, polyvinyl acetate and polyvinyl alcohol, where the sum total of % by weight for components (a) and (b) is 100% by weight. The present invention also provides combinations of distinct components (a) and (b) for conjoint use. The invention further provides polymer membranes comprising the aforementioned polymer blends and also a process for their production and the use of the polymer membranes for producing dialysis filters. The present invention also provides dialysis filters comprising the aforementioned hollow fiber membranes.