Conformational changes of polyelectrolyte chains in solvent mixtures

Abstract

We numerically investigate the behaviors of polyelectrolyte chains in solvent mixtures, taking into account the effects of the concentration inhomogeneity and the degree of the ionization. When changing the interaction parameters between the solvent components, we found a first order transition of the polymer conformation. In the mixing state far from the coexistence curve, the polymers behave as semi-flexible chains. In the phase-separated state, on the other hand, they show compact conformations included in the droplets. As the interaction parameters of the mixture are increased, an inhomogeneous concentration field develops around the polymer and induces critical Casimir attractive interactions among the monomers. The competition between the electrostatic interactions and the critical Casimir ones gives rise to drastic changes in the conformation.