Polyelectrolyte solutions with stickiness between polyions and counterions

Polyelectrolyte solutions are modeled as linear tangent-jointed charged har d-sphere chains and counterions embedded in a continuum medium; the stickin ess between the polyions and the counterions beyond the territorial binding is taken into account as the short-range non-Coulombic perturbation. Expre ssions of thermodynamic properties derived are then consisted of two contri butions. The chain contribution concerns the formation of polyion chains fr om the monomers. The sticky contribution accounts for the additional non-Co ulombic stickiness, which is derived by solving the Ornstein-Zernike integr al equation through the mean-spherical approximation (MSA) and the hypernet ted-chain approximation (HNC). For the model solutions without stickiness b etween the polyions and the counterions, effects of polyion chain lengths, counterion sizes, counterion charges, and the dielectric constants on the t hermodynamic properties are extensively studied. Comparisons of the osmotic pressures for the model solutions with those predicted from Manning's limi ting law (LL), and where possible, with computer simulations are presented. For practical synthetic polyelectrolyte solutions, involving an adjustable parameter responsible for the additional stickiness, experimental thermody namic properties can be described satisfactorily. (C) 1999 American Institu te of Physics. [S0021-9606(99)51809-6].