Highly asymmetric polyethersulfone membranes prepared from a stable, clear, homogeneous solution or stable colloidal dispersion of polyethersulfone are described. The membranes have a porous skin possessing a high density of skin pores with an average diameter of from about 0.001 micron to about 20 microns....http://www.google.com/patents/US5886059?utm_source=gb-gplus-sharePatent US5886059 - Highly asymmetric polyethersulfone filtration membranes
