The interpolymeric specific interaction between proton-donating polymers (PDPs) and proton-accepting polymers (PAPs) was studied by viscometry. The intrinsic viscosities and Schultz-Blaschke constants were measured for the component polymers as well as for the polymeric mixture systems. The estimation of the extent of interpolymeric interaction was done with a new criterion, beta, based on the relationship between the degree of complexation (DA) and the theoretical specific viscosity of the polymeric mixture(eta(sp,m,cal)). This method shows the interpolymeric interaction predictions to be in agreement with those found by a viscosity-enhancement factor. According to the beta criterion and viscosity enhancement factors, the octyl acrylate unit in the PDP/PAP mixture is found to make a positive contribution to the complexation between PDP and PAP attributed to its solvation and van der Waals force between side chains of the octyl acrylate unit on unlike macromolecular chains. beta 2002 Wiley Periodicals, Inc.