Commercial polysulfone (PSf) membranes were crosslinked with a -cyclodextrin-poly (propyleneimine) (-CD-PPI) conjugate which had -CD pendant arms using trimesoyl chloride (TMC) by interfacial polymerization. The morphology and physicochemical properties of the nanofiltration membranes were characterized using Fourier transform infrared/attenuated total reflectance (FT-IR/ATR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and cross-flow filtration system. Water-contact angle, water-intake capacity, and rejection capacities of the membranes were evaluated. The -CD-G4 (generation 4)-PPI-PSf and -CD-G3 (generation 3)-PPI-PSf membranes both exhibited high humic acid rejection of 72% as compared to the commercial PSf which exhibited 57%. The modified membranes were also more hydrophilic (36 degrees to 41 degrees) than PSf (76 degrees). These results suggest that -CD-PPI nanostructures are promising materials for the synthesis of membranes for the removal of humic acid from water. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4428-4439, 2013