Nanoprecipitation for ultrafiltration membranes

Polymer nanoparticles are readily obtainable by rapidly mixing a dilute polymer solution and a poor solvent. The nanoparticles of poly(vinylphenol), poly(vinylidene fluoride), and emeraldine base polyaniline prepared by nanoprecipitation become sticky when their diameters decrease down to a few tens of nanometers, and such polymer nanoparticles spontaneously assemble into rigid fractal networks of the nanoparticles. By filtering these fibrous nanoparticle networks on a microfiltration membrane, ultrafiltration membranes with a thin free‐standing filter cake layer made of nanoparticles are obtainable. The nanoparticle membranes are robust at least up to the applied pressure of 2 MPa and can separate 99% of 10 nm Au nanoparticles from the aqueous dispersion at the flux of more than 1835 L m^?2 h^?1 even at very low pressure difference of 0.08 MPa. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 615–620