Diffusion and Viscosity of Unentangled Polyelectrolytes

Macromolecules, vol. 54, pp. 8088–8103

Abstract

We report chain self-diffusion and viscosity data for sodium polystyrene sulfonate (NaPSS) in semidilute salt-free aqueous solutions measured by pulsed-field gradient NMR and rotational rheometry, respectively. The molecular weight of NaPSS is characterized using five techniques. Relationships between M w and the intrinsic viscosity and diffusion coefficient in excess salt are established. These are helpful for the accurate determination of the molar mass of NaPSS. The observed concentration dependence of η and D are consistent with the Rouse–Zimm scaling model if the monomeric friction coefficient (ζ) is concentration-dependent. The concentration dependence of ζ exceeds that expected from free-volume models of diffusion, and its origin remains unclear, possibly being related to electrostatic effects. Correlation blobs and dilute chains with equivalent end-to-end distances exhibit nearly equal friction coefficients, in agreement with scaling. Viscosity and diffusion data are combined using the Rouse model to calculate the single-chain dimensions of NaPSS in salt-free solution, and the results overpredict direct SANS measurements of the radii of gyration by a factor of ≃1.4.

Authors 4

1. Carlos G. Lopez corresponding Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany

2. Jürgen Linders

   University of Duisburg-Essen

   Affiliation as printed

   Physical Chemistry and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, 45117 Essen, Germany

3. Christian Mayer corresponding

   University of Duisburg-Essen

   Affiliation as printed

   Physical Chemistry and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, 45117 Essen, Germany

4. Walter H. Richtering Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany