Abstract: Molded articles of an aromatic polymer are described having at least a portion of the surface layer of the polymer modified by a heterogeneous reaction of the solid polymer and a reactive solution. The polymer to be treated may contain different repeating units in the said surface layer. The treatment to produce the molded article may comprise casting, injection molding, extending or otherwise shaping the polymer to mold the polymer into a desired shape. The heterogeneous treatment to produce the heterogeneously modified molded article may comprise treating a surface layer of a flat cast sheet in the form of a flat membrane, spirally wound membrane, hollow fiber, or tubular material.

Abstract: Reverse osmosis membranes are manufactured by casting a polysulfone casting composition comprising:(i) an aromatic polysulfone derivative having repeat units, at least an average of about 20% of which are carboxylated and are of the formula I: ##STR1## , wherein each R in each formula is ortho to the sulfone, at least one R in each formula is a carboxyl group with any remainder thereof being hydrogen, and(ii) a solvent for the aromatic polysulfone derivative, then evaporating solvent from the casting composition and then gelling the casting composition into a reverse osmosis membrane. The permeability of the reverse osmosis membrane may be increased by the addition of a non-solvent for the aromatic polysulfone derivative to the casting composition.