INTERACTION OF CHARGED SURFACES WITH GRAFTED POLYELECTROLYTES - A POISSON-BOLTZMANN AND MONTE-CARLO STUDY

We present a Monte Carlo and mean-field study of two charged surfaces with grafted polyelectrolytes, examining the dependence on system parameters of the osmotic pressure as well as intrinsic equilibrium properties of the polyelectrolytes. The polyelectrolyte molecules are modeled as charged monomers connected via suitable bond potentials. The monotonic repulsion between charged surfaces in a simple electrolyte solution, expected from traditional double-layer theory, is not realized in this system. Indeed, we find the force attractive over a wide range of parameter values, with a significant magnitude compared to that of either ordinary double layer or van der Waals forces. The attraction is mainly due to an entropically driven bridging across the gap between the surfaces by the chains, while the attraction due to ion-ion correlation seems to be of minor significance in this system. The mean-field approximation provides a quantitatively correct description of the system, and, most importantly, it responds correctly to changes in parameter space. © 1990, American Chemical Society. All rights reserved.