Professor Ralph Colby is one of the co-authors of the classical textbook "Polymer Physics" (Colby & Rubinstein), and more information about him can be found on his website: http://felix.metsce.psu.edu/rheology/

 The viscosity and relaxation time of polyelectrolyte solutions in high dielectric constant solvents are reported. The effects of polyelectrolyte concentration, polyelectrolyte charge density, solvent dielectric constant, solvent quality and salt concentration are well described by scaling theory. The overlap and entanglement concentrations are apparent from the concentration dependence of viscosity. While the overlap concentration has the expected chain length dependence, the entanglement concentration does not. Semidilute unentangled solutions are described by the Rouse model and a new path to understanding shear thinning in the Rouse model is presented. New data are presented for partially quaternized poly(2-vinylpyridine) in ethylene glycol (EG) and N-methyl formamide

(NMF). EG and NMF are good solvents for the neutral polymer before quaternization, enabling the effects of polyelectrolyte charge density to be studied over an unusually wide range. EG also can be purified to have essentially zero salt ion contaminants,

allowing dilute solutions of high molecular weight polyelectrolytes to be studied in the low salt limit (whereas this is impossible for all aqueous solutions and solutions in NMF). Hence, the scaling model can be fully tested in EG solutions. After multiple distillations,

NMF has even larger quantities of residual salt than distilled water. However, the rheology of polyelectrolyte solutions in NMF can be understood by identifying the concentration at which the number density of free counterions equals the number density

of salt ions. At higher concentrations, the solution viscosity obeys the low salt scaling predictions and at lower concentrations the viscosity obeys the high salt predictions.