A new equation of state of a flexible-chain polyelectrolyte solution: Phase equilibria and osmotic pressure in the salt-free case

摘要

We develop a first-principle equation of state of salt-free polyelectrolytesolution in the limit of infinitely long flexible polymer chains in theframework of a field-theoretical formalism beyond the linear Debye-Hueckeltheory and predict a liquid-liquid phase separation induced by a strongcorrelation attraction. As a reference system we choose a set of two subsystems- charged macromolecules immersed in a structureless oppositely chargedbackground created by counterions (polymer one component plasma) andcounterions immersed in oppositely charged background created by polymer chains(hard-core one component plasma). We calculate the excess free energy ofpolymer one component plasma in the framework of Modified Random PhaseApproximation, whereas a contribution of charge densities fluctuations ofneutralizing backgrounds we evaluate at the level of Gaussian approximation. Weshow that our theory is in a very good agreement with the results ofMonte-Carlo and MD simulations for critical parameters of liquid-liquid phaseseparation and osmotic pressure in a wide range of monomer concentration abovethe critical point, respectively.