Relaxation Times of Flexible Polymer Chains in Solution from Non- Conventional Viscosity Measurements

This work is devoted to the study of the viscosity and relaxation of flexible polymer chains in dilute solutions. Our aim was to determine the relation between the intrinsic viscosity and the relaxation times of the polymer internal normal modes within the bead-spring approach. In the theoretical part we generalize the Zimm theory of the polymer dynamics by taking into account the permeability of the solvent into the polymer coil interior and the hydrodynamic interactions between different coils. For theta solvents the polymer relaxation is described as depending on the draining parameter and the concentration of the coils. Using the calculated relaxation times, the intrinsic viscosity has been obtained. The free-draining (Rouse) and non-draining (Zimm) expressions for this quantity follow from the theory as special cases of infinite and zero permeability, respectively. In the experimental part we studied the viscosity of high-molecular poly(Nvinyl-2-pyrrolidone) water solutions at different temperatures down to such low concentrations when conventional capillary viscosimetry fails to probe the viscosity without a complicated additional treatment of the data. Using a new Couettetype viscosimeter with a magnetically suspended rotor allowed us to directly determine the intrinsic viscosity. It notably differs from the previous values reported in the literature. By comparison of the data to the theory, the quantities used in the description of the universal polymer behavior in solution have been estimated.