Gradient Dependence of the Intrinsic Viscosity of Linear Macromolecules

Abstract

The decrease of intrinsic viscosity with increasing gradient was found with all linear macromolecules investigated at high enough molecular weight irrespective of the solvent. But experiments do not agree on the power of the gradient to which the deviations from the zero value are proportional. Exponents ½, 1, and 2 have been proposed to fit experimental data. The necklace model with hydrodynamic interaction yields suitable gradient dependence of the intrinsic viscosity only if either the molecule has a nonvanishing rigidity or the anisotropy of the hydrodynamic interaction is explicitly considered. Since the first effect decreases with increasing M, very likely most of the observed gradient dependence has to be attributed to the second one which is intrinsically connected with the statistical shape of the molecular coil and the character of the hydrodynamic forces.