Simulations and integral equation results are presented for a model partly quenched system composed of monovalent ions. Static and dynamic properties of the system are explored using the replica Ornstein–Zernike theory in the hypernetted chain approximation and Brownian dynamic simulations. The model system consists of two subsystems: one is a collection of charged obstacles (matrix), and the other is an invading electrolyte. The overall system is electroneutral, while the subsystems are not. Charged species are represented by Lennard–Jones spheres of equal size, with either positive or negative charge in the center. The solvent is treated as a continuous dielectric. The purpose of this study is to correlate the mobility of ions (selfdiffusion coefficients) with their individual activity coefficients.
COBISS.SI-ID: 36498181
Enthalpies of dilution of aqueous solutions of aliphatic 6,12- and 12,12-ionene bromides and fluorides and enthalpies of mixing with low molecular weight salts, such as Naf and NaBr, are determined. The comparison with theoretical results, based on the Poisson–Boltzmann cell model, is presented. The theory predicts for the enthalpy of dilution to be exothermic and the enthalpy of mixing endothermic, while experiments show that signs of the heat effects depend on the nature of the counterion of the added salt, as also on the hydrophobicity (numbers x, y of methylene groups) of the ionene. We show that the salts when ordered by heat effects produced by mixing of NaF and NaBr with 3,3, 6,9, or 6,12-ionene fluorides and bromides follow the opposite ordering than in the case when the same alkali halide salts are mixed with more hydrophobic 12,12-ionene salts.
COBISS.SI-ID: 36662021
Transport and binding capabilities in aqueous solutions of 3,3, 6,6, and 6,9-ionene fluorides and bromides at 298 K were explored through the experimentally determined values for transport numbers of counterions and polyion constituents, along with the data for electrical conductivity in these solutions. Within the association theory, the fractions of free counterions and the effective linear charge densities of polyions were calculated. It was determined that binding of the counterions to the polyion critically depends (i) on charge density of the polyion and (ii) on the chemical nature of the counterion in question. The effects of the charge density are the strongest in solutions of ionene bromides. Differences in the behavior of solutions of ionene fluorides and bromides are the consequence of different hydration capabilities of these ions. The effective linear charge density was found to be much lower than predicted from structural parameters of ionenes.
COBISS.SI-ID: 36602373
Enthalpies of mixing of aliphatic 3,3 and 6,6-ionene fluorides with low molecular weight salts (sodium formate, acetate, nitrate, chlorate(V), and thiocyanate), all dissolved in water, were determined. Electrostatic theory, predicted the enthalpy of mixing to be endothermic in all the cases, while experiments showed that this is not always true. When an aqueous solution of 3,3-ionene-fluoride was mixed with a solution of NaF (or formate and acetate) in water, the effect was indeed endothermic. For all other salts heat was released upon mixing. The enthalpy of mixing was strongly correlated with the enthalpy of hydration of the counterion of the low molecular weight salt. A lyotropic series, similar to that of Hofmeister, was obtained. To examine also the effect of coions, ionene bromides were titrated with tetramethyl,-tetraethyl,-or tetrapropylammonium bromides. The enthalpy was exothermic for all mixtures while, somewhat unexpectedly, the coion-specific effect was quite strong.
COBISS.SI-ID: 35925509
Aqueous solutions of x,y-ionenes with bromide and fluoride counterions have been investigated using small angle neutron scattering for the first time. We conclude that despite the hydrophobicity of the hydrocarbon chain separating charged centers on ionenes, these chains behave as hydrophilic. The most important observation is that in contrast to Br ionenes, the polyelectrolyte peak remains at all concentrations studied for the single F ionene investigated. This strong counterion effect is rationalized in terms of the different hydrating properties and ion pairing in the case of bromide and fluoride ions.
COBISS.SI-ID: 36222725