The radiation-induced graft copolymerization of N-vinyl-2-pyrrolidone (NVP) onto polypropylene films was investigated using the mutual method. The grafted polymer was modified with prepared alpha,beta-unsaturated nitrile (Scheme 1). The water uptake of the grafted and modified grafted films was found to increase with the degree of grafting. It was observed that the swelling behavior of the modified grafted films with alpha-cyano-beta-phenyl crotononitrile improved more than that of the film grafted and modified grafted with alpha-cyano-beta-(2-thienyl)crotononitrile or alpha-cyano-beta-(2-pyridyl)crotononitrile. The modification process for the grafted substrate was confirmed by IR spectroscopy. No significant improvement was observed in thermal stability for the modified grafted films compared to the grafted films. Scanning electron microscopy (SEM) of the grafted and modified grafted membranes heated to 150 degrees C showed change in the structure and morphology. Improvement in the hydrophilicity and morphology of these membranes with carbonitriles may increase the permeability of those membranes for some practical applications. (C) 2000 John Wiley & Sons. Inc.