Novel thermosensitive, cationic polyelectrolyte was obtained by grafting N-vinylformamide onto hydroxypropylcellulose followed by the hydrolysis of the formamide groups to the amine groups. The effect of the ionic strength on the lower critical solution temperature of the polymers was studied. The interactions of the polymers with sodium dodecyl sulfate (SDS) as a model anionic surfactant were studied. It was found by the measurements of the light scattering and fluorescence spectroscopy that the graft copolymers obtained strongly interact with SDS with the formation of polymer-surfactant complexes. The values of critical association concentration (cac) of these polymer-surfactant systems were found to be of the order of 10(-5) mol/dm(3) at pH = 6.5 and of the order of 10(-6) mol/dm(3) at pH = 2.5. The polymer was shown to be potentially useful for the purification of water from anionic surfactants. (c) 2007 Wiley Periodicals, Inc.