Ultrasoft primitive model of polyionic solutions: structure, aggregation, and dynamics

Abstract

We introduce an ultrasoft core model of interpenetrating polycations and polyanions with continuous Gaussian charge distributions, to investigate polyelectrolyte aggregation in dilute and semi-dilute, salt-free solutions. The model is studied by a combination of approximate theories (random phase approximation and hypernetted chain theory) and numerical simulations. The calculated pair structure, thermodynamics, phase diagram and polyion dynamics of the symmetric version of the model (the "ultrasoft restricted primitive model" or UPRM) differ from the corresponding properties of the widely studied "restricted primitive model" (RPM) where ions have hard cores. At sufficiently low temperatures and densities, oppositely charged polyions form weakly interacting, polarizable neutral pairs. The clustering probabilities, dielectric behavior and electrical conductivity point to a line of sharp conductor-insulator transitions in the density-temperature plane. At very low temperatures the conductor-insulator transition line terminates near the top of a first order coexistence curve separating a high-density, liquid phase from a low-density, vapor phase. The simulation data hint at a tricritical behavior, reminiscent of that observed of the two-dimensional Coulomb Gas, which contrasts with the Ising criticality of its three-dimensional counterpart, the RPM.

17 pages, 19 figures

References in corpus (10)

• Diamondoid Molecules
• Effective interactions between electric double-layers
• Accurate effective pair potentials for polymer solutions
• Universality class of criticality in the restricted primitive model electrolyte
• Complex coacervation: A field theoretic simulation study of polyelectrolyte complexation
• Computer simulation of fluid phase transitions
• Critical behavior of the restricted primitive model revisited
• Ion association in low-polarity solvents: comparisons between theory, simulation, and experiment
• Dipolar origin of the gas-liquid coexistence of the hard-core 1:1 electrolyte model
• Computer simulations of the restricted primitive model at very low temperature and density

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• Mean-field electrostatics beyond the point-charge description
• Phase behaviour and the random phase approximation for ultrasoft restricted primitive models
• Liquid-Vapor Transition and Critical Behavior of The Ultrasoft Restricted Primitive Model of Polyelectrolytes : a Monte Carlo Study
• Structure and dynamics of coupled viscous liquids
• Mean-field theory of active electrolytes: dynamic adsorption and overscreening
• GCMe: Efficient implementation of the Gaussian core model with smeared electrostatic interactions for molecular dynamics simulations of soft matter systems
• Two-component Gaussian core model: strong-coupling limit, Bjerrum pairs, and gas-liquid phase transition
• Gas-liquid critical point of the ultrasoft restricted primitive model from analytic theory