Semi-empirical model for polyelectrolyte intrinsic viscosity as a function of solution ionic strength and polymer molecular weight

Elements of Odijk-Skolnick-Fixman and Yamakawa-Fujii polymer solution theories have been modified to create a new model that correlates flexible coil polyion intrinsic viscosity behavior with solvent and polymer properties. A new dimensionless viscosity is derived and is successfully related to the dimensionless ratio of Debye-Hückel screening length to polyion charge spacing and the degree of polymerization. The model has been applied to intrinsic viscosity data reported in the scientific literature and to data collected in our laboratory, all using sodium chloride solutions ranging in ionic strength. Multiple molecular weight fractions of six compositionally different polyelectrolytes were used to obtain 73 intrinsic viscosity versus ionic strength data points for model analysis. Regression analysis was applied to empirically determine the relationships between the dimensionless groups. The resulting model equation was found statistically adequate in describing the entire data set.