A viscosimetric method has been used to study the interpolymer association between poly(vinyl alcohol) (PVA) and poly(sodium styrene sulfonate) (PSSNa) in aqueous solution. At constant molecular weight of PSSNa, it was found that, the PVA and PSSNa associations were improved with the decrease of molecular weight of PVA and the decrease of its hydrolysis degree. The measurement of intrinsic viscosity [eta] and the determination of Huggins associative coefficient K-H of different PVA samples were used to select the most appropriate PVA sample, which leads to homogeneous polymer-polymer mixtures (PVA with hydrolysis degree 87-89%, molecular weight 124,000-186,000 g/mol, intrinsic viscosity [eta] 1.02 dL/g, and Huggins associative coefficient K-h.ass = 0.76). The obtained results show that the interpolymer association between PVA and PSSNa, in aqueous solution, is mainly due to intermolecular hydrogen bonds between hydroxyl groups of PVA and sulfonate groups of PSSNa. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 3395-3401, 2009