Salt Effect on Osmotic Pressure of Polyelectrolyte Solutions: Simulation Study

Abstract

Abstract:We present results of the hybrid Monte Carlo/molecular dynamics simulations of the osmotic pressure of salt solutions of polyelectrolytes. In our simulations, we used a coarse-grained representation of polyelectrolyte chains, counterions and salt ions. During simulation runs, we alternate Monte Carlo and molecular dynamics simulation steps. Monte Carlo steps were used to perform small ion exchange between simulation box containing salt ions (salt reservoir) and simulation box with polyelectrolyte chains, counterions and salt ions (polyelectrolyte solution). This allowed us to model Donnan equilibrium and partitioning of salt and counterions across membrane impermeable to polyelectrolyte chains. Our simulations have shown that the main contribution to the system osmotic pressure is due to salt ions and osmotically active counterions. The fraction of the condensed (osmotically inactive) counterions first increases with decreases in the solution ionic strength then it saturates. The reduced value of the system osmotic coefficient is a universal function of the ratio of the concentration of osmotically active counterions and salt concentration in salt reservoir. Simulation results are in a very good agreement with osmotic pressure measurements in sodium polystyrene sulfonate, DNA, polyacrylic acid, sodium polyanetholesulfonic acid, polyvinylbenzoic acid, and polydiallyldimethylammonium chloride solutions.

Magnesium, Calcium, Potassium, Sodium, Phosphorus, Selenium, Zinc, and Chromium Levels in Alcohol Use Disorder: A Review

“…Sodium is responsible for maintaining basic vital functions. It is involved in maintaining water and electrolyte balance [ 120 ], acid-base [ 121 ], osmotic pressure [ 122 ], transport of amino acids, carbohydrates and vitamins [ 123 ] serotonin (SERT), dopamine, noradrenaline, GABA [ 124 , 125 ], excitability neuromuscular [ 126 ], and conduction of nerve impulses [ 127 ]. Physiological sodium levels in the plasma range from 135 to 145 mM/L ( Table 3 ).…”

Collagen intrafibrillar mineralization as a result of the balance between osmotic equilibrium and electroneutrality

“…The net result of the Gibbs-Donnan effect is that more water moves into the extrafibrillar compartment than would be predicted on the basis of oncotic pressure of the PAH molecules alone. Partitioning of osmotically-active counterions and salt ions across membrane impermeable to polyelectrolyte chains to establish Gibbs-Donnan equilibrium 36 has been exhaustively modelled using Monte Carlo simulations 37 .…”

The Effect of Molar Mass and Charge Density on the Formation of Complexes between Oppositely Charged Polyelectrolytes

“…For instance, at 1M ionic strength for PAMAMPS, we can evaluate from the work of Trizac et al [ 44 ] a shift of ξ * from unity (Manning) to ~0.65. Moreover, Carrillo et al [ 45 ] showed using hybrid Monte-Carlo/molecular dynamics simulations that the fraction of condensed counter-ions decreases with increasing ionic strength, while Muthukumar [ 46 ] predicted an opposite behavior. Due to the complexity of the counter-ions condensation phenomenon, which depends on many physico-chemical parameters (ionic strength, polymer concentration, polymer backbone size, charge density parameter), we restricted our estimation to the framework of Manning theory.…”