In this paper, we provide a simplified method to prepare functional polyethersulfone (PES) membranes with pH sensitivity and ion-exchange capacity by blending cross-linked poly (acrylic acid) (PAA) submicrometer-scale gels. The PAA gels were synthesized through the solution polymerization of acrylic acids in dimethylacetamide (DMAC) under strong agitation, the size of the gels ranged from about 250 to 3000 nm. With the increase of the agitation rate, the gel size increased. The PAA gel solution can be directly blended with PES solution (using DMAC as the solvent) to prepare membrane using a phase separation technique. After blending the PAA gels. the morphology of the PES membrane was substantially altered: and the finger-like structure became a sponge-like structure. The blended PES membranes showed evident pH sensitivity and pH reversibility; and the pH-valve effect was observed at pH between 3 and 8. With the increase of the gel size, the pH sensitivity increased; and with the increase of the gel amount blended in the membrane, the water flux increased under acid conditions. The permeability results suggested that the flux of acidic amino acid solution was higher than basic amino acid solution. The Cu2+ ion-exchange experiment indicated that the membranes could bind metal ions, and had potential to be used as ion-exchange membranes. (C) 2009 Elsevier B.V. All rights reserved.