In this study, a novel polyethersulfone (PES) hollow fiber membrane with pH-sensitivity was prepared using a copolymer of poly(methyl methylacrylate-co-4-vinyl pyridine) (P(MMA-4VPy)) as an additive. The copolymer was synthesized via free radical solution polymerization, and characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The PES/P(MMA-4VPy) membranes showed excellent pH-sensitivity and pH-reversibility and exhibited good Cu(II) ion adsorption property. Furthermore, the effect of Cu(II) ion adsorption on the membrane pH-sensitivity was investigated. (C) 2012 Elsevier B.V. All rights reserved.