Macromolecules 1996,28, 1859-1871 1869 Scaling Theory of Polyelectrolyte Solutions

ABSTRACT: We extend and generalize the scaling picture of de Gennes et al. and Pfeuty to both unentangled and entangled regimes of intrinsically flexible polyelectrolyte solutions. In semidilute solution the electrostatic persistence length of a polyelectrolyte is assumed to be proportional to the Debye screening length. If the salt concentration is low, the unentangled semidilute concentration regime spans three to four decades in polymer concentration. In this regime the dynamics of the chain is Rouse-like with viscosity weakly increasing with concentration 17- c112 (Fuoss law), relaxation time decreasing with concentration T R ~ ~ ~ ~ - c-l12, and diffusion coefficient independent of concentration. Polyelectrolytes should form entanglements a t the same relative viscosity as neutral polymer solutions (17 = 5 0 ~ ~ ). In the entangled reeime of salt-free Dolvelectrolvtes we Dredict the viscositv n- c312. relaxation time to be indeDendent of Y &. I concentration, and diffusion coefficient Dself-experiments. 1