A Semi-Empirical Approach to the Viscosities of Polyelectrolyte Solutions

摘要

The concentration dependence of a number of polyelectrolytes was found to be adequately described by an equation eta(sp)/c = eta(infinity) x (1 + k/sq root of c)) as long as the concentration is not too low. The parameter eta(infinity) represents the intrinsic viscosity of the well-shielded polyion and corresponds to values of (eta) determined in salt solutions and may possibly correspond to the theory of Harris and Rice on polyion expansion. Heuristic arguments based in part on the work of Katchalsky, et al, lead to a definite expression for the parameter k in terms of molecular properties. The result shows that the above equation is valid only for strong polyelectrolytes with the constant activity coefficients of counterion. The calculated values of k agree well with experiment except when specific intramolicular interactions (e. g., internal hydrogen bonding) occur. For highly charged polyions one finds surprisingly, that k depends only on the properties of the polymer backbone and not on electrical properties. (Author)