The present application is generally directed towards polyacrylonitrile— (PAN—) based, amphophilic graft copolymers, for example, for the production of membranes for liquid filtration. In one aspect, the present invention provides systems and methods for preparing high flux, fouling resistant nanofiltration membranes whose pore size can be readily tuned. In some cases, microphase separation of a graft copolymer comprising a backbone comprising polyacrylonitrile (PAN) and hydrophilic side-chains is used. In some cases, nanochannels of tunable width are formed, which may give the membrane permselective properties and/or anti-fouling character. In some cases, a copoylmer may be used as an additive in the immersion precipitation casting of ultrafiltration or microfiltration membranes. In certain instances, the additive can segregate to the membrane exterior and/or pore surfaces, e.g., due to favorable interactions between the hydrophilic side chains and the surrounding environment, which may create a surface that resists fouling, e.g., by biological molecules.