The dependence of the viscosity on the concentration of sodium carboxymethylcellulose in aqueous solutions

Abstract

The Huggins coefficient, k′, was measured for three fractions of sodium carboxymethylcellulose by an iso-ionic dilution technique for ionic strength Ie from 0.1 M to 0.00001 M. At Ie = 0.1 M , k′ was approximately 0.5. However, k′ increased to values as high as 29 at lower ionic strengths. Such substantial increases of k′ were produced by the increased interparticle repulsion at low ionic strength. A model of the collision doublet is proposed in which the hydrodynamic compressive force and the electrostatic repulsive force are in equilibrium. As the ionic strength is lowered, the increased electrostatic potential of the molecule causes an increase in the axial ratio of the doublet and thus produces an increment in k′. A quantitative treatment is given in which the electrostatic potential calculated from the increment in k′ is compared with values computed by means of the equations for the potential of a polyelectrolyte.