Thin composite nanofiltration membranes with improved thermal stability were prepared by coating sulfonated copoly (phthalazinone biphenyl ether sulfone) (SPPBES) on poly (phthalazinone ether sulfone ketone) ultrafiltration support membranes. The effects of polymer concentration, degree of sulfonation of SPPBES, crosslinking agent, curing treatment temperature and curing time on the performance of composite membranes were investigated. The membrane prepared under the optimum condition exhibited a permeate flux of 73 L/m(2)h and 84% rejection of Na2SO4 at 1.0 MPa and 20 degrees C. Moreover, these membranes showed good stability against chemical attack and high tolerance to chlorine. When the temperature of feed solution increased from 20 to 90 degrees C, solution permeate flux increased three-fold while the rejection of the membrane decreased by 2%. (C) 2013 Elsevier B.V. All rights reserved.