A membrane comprising: a) a first layer comprising a first polymer or a fourth polymer having ionic groups of polarity opposite to the polarity of the ionic groups of the third polymer; b) a second layer comprising a second polymer having ionic groups of polarity the same as the polarity of the ionic groups of the third polymer; and c) a third layer comprising a co-continuous polymeric network of (i) a third polymer having ionic groups and a network of pores; and (ii) a fourth polymer having ionic groups of polarity opposite to the polarity of the ionic groups of the third polymer; wherein layer c) is interposed between layer a) and layer b) and the third polymer is obtainable by a process comprising phase separation of the third polymer from a curable composition used to prepare the third polymer.

A low-pressure high-flux hollow fiber nanofiltration (NF) membrane, and a preparation method and use thereof are provided. The low-pressure high-flux hollow fiber NF membrane includes a base membrane and a negatively-charged separation layer formed on a surface of the base membrane, where a material of the separation layer is a crosslinking product of a negatively-charged sulfonated polymer. The low-pressure high-flux hollow fiber NF membrane of the present disclosure solves the technical problem that the hollow fiber NF membranes in the prior art are difficult to have both high performance and low energy consumption.

A polymer film comprising anionic groups and 0.008 to 25 mg/g of each of components (a) and (b): (a) a crosslinking agent which is free from fluoro groups and comprises a group of Formula (I); and (b) a non-ionic crosslinking agent; Formula (I) wherein M.sup.+ is a cation and * indicates the attachment points to other elements of the crosslinking agent.

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