COMPUTER-SIMULATION OF SEMIDILUTE POLYELECTROLYTE SOLUTIONS

We use Monte Carlo simulation methods to study the conformational properties of flexible partially ionized polyelectrolyte chains and the ordering of the polyelectrolyte chains, for polyelectrolyte concentrations where chain-chain interactions start to become important. In this model the ionic and solvent degrees of freedom are frozen and the charges on the polyelectrolyte chains interact via a screened Coulomb interaction of Debye-Hückel form. Our simulations are restricted to polyelectrolyte ionizations and added-salt concentrations where we know that the screening model is not an unreasonable approximation. For semi-dilute polyelectrolyte concentrations we observe some local anisotropy with some alignment between the nearest polyion chains. This alignment only exists for small polyion separations and generally the chains are isotropically distributed and oriented with respect to one another. The observed interchain correlation at small separation distances disappears for dilute polyelectrolyte concentrations below the overlap threshold concentration c*, and also for high polyelectrolyte concentration where interactions between polyions beyond the nearest neighbours begin to become important. For polyelectrolyte concentrations above this value the results for the two added salt concentrations of 0.1 and 0.01 mol dm-3 are almost identical. © 1990.