A poly(vinylidene fluoride)-graft-poly(N-isopropylacrylamide) (PVDF-g-PNIPAAm) copolymer was synthesized, and flat-sheet membranes were prepared via the phase-inversion method with N,N-dimethylformamide (DMF) as the solvent and water as the coagulation bath. The effects of the coagulation-bath temperature on poly(vinylidene fluoride) (PVDF)/DMF/water and PVDF-g-PNI-PAAm/DMF/water ternary systems were studied with phase diagrams. The results showed that the phase-separation process could be due to the hydrophilicity/hydrophobicity of poly(N-isopropylacrylamide) at low temperatures, and the phase-separation process was attributed to crystallization at high temperatures. The structures and properties of the membranes prepared at different coagulation-bath temperatures were researched with scanning electron microscopy, porosity measurements, and flux measurements of pure water. The PVDF-g-PNIPAAm membranes, prepared at different temperatures, formed fingerlike pores and showed higher water flux and porosity than PVDF membranes. In particular, a membrane prepared at 30 degrees C had the largest fingerlike pores and greatest porosity. The water flux of a membrane prepared in a 25 degrees C coagulation bath showed a sharp increase with the temperature increasing to about 30 degrees C. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116:1005-1009, 2010