Thin film composite (TFC) membranes were prepared from sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) as a top layer coated onto poly(phthalazinone ether sulfone ketone) (PPESK) ultrafiltration (UF) support membranes. The effects of different preparation conditions such as the SPPESK concentration. organic additives, solvent. degree of substitution (DS) of SPPEK and curing treatment temperature and time on the membrane performance were studied. The SPPESK concentration in the coating solution was the dominant factor for the rejection and permeation flux. The TFC membranes prepared from glycerol as an organic additive show better performance, then those prepared from other additives. The rejection increased and the flux decreased with increasing curing treatment temperatures. The salt rejections of the TFC nanofiltration (NF) membranes increased in the order MgCl2 < MgSO4 < NaCl < Na2SO4. TFC membranes showed high water flux at low pressure. SPPESK composite membranes rejections for a 1000 mg L-1 Na2SO4 feed solution was 82%, and solution flux was 68 L m(-2) h(-1) at 0.25 MPa pressure. (C) 2004 Elsevier B.V. All rights reserved.