A membrane (m) comprising a sulfonated poly(arylene ether sulfone) polymer (sp) and a non-sulfonated poly(arylene sulfone) polymer (p)

A membrane comprising a blend of

• (A) a sulfonated poly(arylene ether sulfone) polymer and
• (B) a non-sulfonated poly(arylene sulfone) polymer, wherein the membrane has a minimal pore diameter of <5 nm and a pure water permeation of >50 kg/(h m2 bar) and wherein the membrane is a nanofiltration membrane, wherein the average pore diameter is determined by gas adsorption-desorption experiments with nitrogen and Harkins-Jura analysis and rejection of diluted poly(ethylene oxide) solutions with a molecular weight of 8 000 g/mol or diluted rose Bengal with a molecular weight of 1 017 g/mol, and the pure water permeation is determined using a pressure cell with a diameter of 74 mm using ultrapure water (salt-free water, filtered by a Millipore UF-system) at 23° C. and 1 bar water pressure, wherein
• the membrane comprises from 15 to 80% by weight of the sulfonated poly(arylene ether sulfone) polymer, based on the total weight of the membrane, and wherein
• the sulfonated poly(arylene ether sulfone) polymer comprises units of formula (III)
• and/or formula (IV)

A monolithic film comprising

• (A) a sulfonated poly(arylene ether sulfone) polymer and
• (B) a non-sulfonated poly(arylene sulfone) polymer,
• wherein the monolithic film has a contact angle of 63 to 77°, wherein the contact angle is determined by time-resolved automated image analysis at 23° C. placing 8 to 10 drops of deionized water on the sample, and wherein
• the monolithic film comprises from 15 to 80% by weight of component (A) and from 20 to 85% by weight of component (B), each based on the total weight of the monolithic film.