Viscosities of Polyelectrolytes

Stigter, D, Ionic Charge Effects on the Sedimentation Rate and Intrinsic Viscosity of Polyelectrolytes. T7 DNA, Macromolecules 18, 1619, 1985. 

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

Figure 6. Effect of C12 content on reduced viscosity of polyelectrolytes. Key 1, polyivinyl-N-ethylpyridinium bromide) 2, 6.75% polysoap 3, 13.6% poly soap 4, 28.5% poly soap 5, 37.9% polysoap. Reproduced from ref. 8. Copyright 1954 American Chemical Society.)...

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. 

Still the coil expansion and the intrinsic viscosity depend on the salt concentration, even for a linear curve progression. For this reason, intrinsic viscosities of polyelectrolytes should be always accompanied by the salt concentration that they were determined at. This is extremely important for the [/j]-M-relationships described in chapter 6. As one can see in Fig. 6.11 theses relationships change for the same polymer, depending on the salt concentration at which the intrinsic viscosity was determined. 

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... 

Flory, P.J. and Osterheld, J.E., Intrinsic viscosities of polyelectrolytes polyacrylic acid, /. Phys. Chem., 58, 653, 1954. 

This section could have followed section 1 in this chapter. The reason for placing it here is that the concepts and derivations developed in section 2 are needed for deriving the viscosity equation for polymeric electrolytes (polymer solutions) and polymer melts. Similar to the previous two sections, the viscosity of polyelectrolytes and polymer melts without an external electric field are discussed first, and then the viscosity of those materials under an external electric field or having strong surface charges are focused upon thereafter. 

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... 

While it may be argued that the retention data may show a salinity effect (compare Cores 52 and 55, Table 2), this effect appears smaller than other observations. For some systems, Holland and Eirich have shown the resistance factor to be directly related to the intrinsic viscosity. The effect of brine concentration on the intrinsic viscosity of polyelectrolytes has been shown to decrease with increasing ionic strength. Consequently, the lack of a significant brine effect on measured resistance factors is explainable by the... 

Pavlov, G. M., Gubarev, A. S., Zaitseva, I. L, and Sibileva, M. A. 2006. Determination of intrinsic viscosity of polyelectrolytes in salt-free solutions. Russ. J. Appl. Chem. 79 1407-1412. 

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