Novel polyion complexes films of chitosan and quarternized poly(4-vinyl-N-carboxymethylpyridine) containing zwitterion structure units were prepared by casting method. The aim of this work was to produce a hydrophilic film with the potential use as a hydrophilic membranes of the types used in membranes distillation and osmotic distillation for separating azeotropic, close-boiling, and aqueous organic mixtures. Their structure and properties were studied by infrared, wide-angle X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, tensile tester, and swelling measurements. The results indicated that polyion complexes occurred between chitosan and quarternized poly (4-vinyl-N-carboxymethylpyridine) containing zwitterion structure units. The thermostability of these blends decreased with the increase of quarternized poly(4-vinyl-N-carboxymethylpyridine) content. Initially, appreciable improvement in tensile strength and breaking elongation were achieved with increase of quarternized poly(4-vinyl-N-carboxymethyl-pyridine) content to 30%, the maximum value of 46.65 MPa tensile strength and 25.67% breaking elongation were achieved, respectively. The maximum degree of swelling was achieved when the weight ratio of chitosan versus poly(4vinyl-N-carboxymethylpyridine) was 50 : 50. Meanwhile, the relationship between their structure and properties was also discussed. (c) 2007 Wiley Periodicals, Inc.