Relaxation Times of Flexible Polymer Chains in Solution from NonConventionalViscosity Measurements

摘要

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 internalnormal modes within the bead-spring approach. In the theoretical part we generalize the Zimm theory of the polymer dynamicsby taking into account the permeability of the solvent into the polymer coil interior and the hydrodynamic interactionsbetween different coils. For theta solvents the polymer relaxation is described as depending on the draining parameterand the concentration of the coils. Using the calculated relaxation times, the intrinsic viscosity has been obtained. Thefree-draining (Rouse) and non-draining (Zimm) expressions for this quantity follow from the theory as special cases of infiniteand 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 capillaryviscosimetry fails to probe the viscosity without a complicated additional treatment of the data. Using a new Couettetypeviscosimeter with a magnetically suspended rotor allowed us to directly determine the intrinsic viscosity. It notablydiffers from the previous values reported in the literature. By comparison of the data to the theory, the quantities used inthe description of the universal polymer behavior in solution have been estimated.