DILUTE-SOLUTION BEHAVIOR OF CYCLIC AND LINEAR POLYELECTROLYTES

Viscosities and diffusion coefficients of dilute solutions of molecular weight matched cyclic and liner poly (2-vinyl pyridine) samples with molecular weights ranging from 2.8 x 10(4) to 1.0 x 10(5) have been measured under conditions where the polymer can be charged by protonation. Limiting conditions of high charge density and full electrostatic screening with high acid concentration solutions show expected normal polymer behavior in extrapolations to the intrinsic viscosity and infinite dilution diffusion coefficients. By employing weakly acidic solvents, large reduced viscosities, typical of polyelectrolytes in low salt solutions are observed. A pronounced maximum in reduced viscosity occurs at a concentration which is independent of molecular weight and topology. Values of the reduced viscosity are lower for the cyclic samples over all concentrations investigated. Independent pH titrations are used to calculate polyion charge density and electrostatic screening lengths. Possible origins of the viscosity maxima are explored.