Effect of hydrodynamic field of the conformation of polyelectrolyte in the coil-globule transition region

The effects of solution concentration, solvent composition, and velocity gradient on the kinetics of coil-globule transition were studied for three samples of high-molecular-mass polyelectrolyte poly(dimethylaminoethyl methacrylate) (M(w) = 28 x 10(6), 20 x 10(6), and 15 x 10(6)). Variation of reduced viscosity with composition of water-acetone solvent gamma (gamma is the fraction of acetone in the solvent) and shear gradient g was studied in the range of solution concentrations extending from 6 x 10(-2) to 5 x 10(-4) g/dl. At g approximate to 1000 s(-1) and gamma less than or equal to 0.50, the plot of reduced viscosity versus concentration is linear, whereas, at gamma > 0.50 in the concentration range below that conforming to the criterion c[eta] approximate to 1, the viscosity drastically decreases, and the corresponding plot deviates from linearity. This phenomenon may be related to the rearrangement of intra- and intermolecular interactions when concentrations at which the number of intermolecular contacts significantly decreases are attained and to the formation of local compaction nodes on a macromolecular chain induced by the applied hydrodynamic field. For small g, the dependence of reduced viscosity on concentration is most pronounced at gamma = 0.50; as gamma increases, the dependence gradually becomes less prominent. At gamma = 0.75, the examined polyelectrolyte undergoes the coil-globule transition, and the magnitude of intrinsic viscosity is independent of the velocity gradient.