Viscosity of polyelectrolyte solutions

Tam, K. C. and Tiu, C. 1993. Improved correlation for shear-dependent viscosity of polyelectrolyte solutions. J. Non-Newtonian Fluid Mech. 46 275-288. 

Branched polymers in good solvents Intrinsic viscosity of polyelectrolyte solutions... 

INTRINSIC VISCOSITY OF POLYELECTROLYTE SOLUTIONS 45 1.7 INTRINSIC VISCOSITY OF POLYELECTROLYTE SOLUTIONS 1.7.1 Role of Electrostatic Interactions... 

The highly nonlinear concentration dependence evident in Figure 1.9 makes determination of the intrinsic viscosity by extrapolation of tjsp/c data via Eqs. (1.24) and (1.25) impossible. Cohen and Priel [1990] report observing that linear concentration dependence is observed at concentrations substantially below Cmax. allowing determination of [ ]. Theoretical analysis [Nishida et al., 2001, 2002] suggests that the dominant contribution responsible for the appearance of the peak in the / sp/c versus c plots comes from the intermolecular electrostatic repulsions between polyions. Based on this idea, Nishida et al. [2002] propose a method to determine the intrinsic viscosity of polyelectrolyte solutions at very low ionic strength, by assuming additivity in the contributions of intra- and intermolecular interactions that is. 

The concentration dependence of the viscosity of polyelectrolyte solutions has been discussed by several authors [Cohen et al., 1988 Cohen and Priel, 1990 Borsali et al., 1992, 1994 Antonietti et al., 1997]. Several groups [Borsali et al 1992, 1994 Antonietti et al., 1997] have used the mode-mode coupling approximation of Hess and Klein [1983]. In the weakly charged polyelectrolyte limit, the latter formulation leads to an expression for the time-dependent viscosity of the form [Borsali et al., 1992]... 

Nishida, K., Kaji, K., and Kanaya, T., Theoretical calculation of reduced viscosity of polyelectrolyte solutions. Polymer, 42, 8657-8662 (2001). 

Usually, flocculating agents are received as solids or thick liquids. They are dissolved or diluted to low concentrations because the viscosity of polyelectrolyte solutions can be quite high. This can make it difficult to wet and disperse the material properly. The result of improper dispersion is the formation of lumps that dissolve extremely slowly and that are not effective in the process. A supplier reports that dilute solutions of a flocculant often give superior results and that multiple-point addition of the flocculant can improve its contact with the brine [91]. The polymers are sensitive to shear, and the agitation process must be chosen with care. Turbulence at the addition point(s) should provide good dispersion but not break the floes. 

The viscosity of polyelectrolyte solutions varies dramatically with ionic strength and pH. The theory and experimental situation for these solutions is outlined in Section 10.4... 

Contrary to Eq. (2,33) the reduced viscosity of polyelectrolyte solutions is observed to decrease strongly with increasing concentration at low ionic strength. In the late 1940s this experimental fact inspired Fuoss and Strauss [67-70] to propose their famous empirical linearization of the reduced viscosity... 

In 1987 Witten and Pincus [71] presented a theory for the viscosity of polyelectrolyte solutions which was derived for concentrations near the overlap concentration. Again, at the limit Cp > c, the Fuoss law ti, oc c was obtained. Later Rabin [72] derived a similar relation (for the viscosity of poly-electrolyte solutions) on the basis of the theory by Hess and Klein. With some bold simplifications Rabin arrived at... 

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