We extend our previous study [J. Chem. Phys. 138, 204907 (2013)] to quantify the screening properties of four mesoscale smoothed charge models used in dissipative particle dynamics. Using a combination of the hypernetted chain integral equation closure and the random phase approximation, we identify regions where the models exhibit a real-valued screening length, and the extent to which this agrees with the Debye length in the physical system. We find that the second moment of the smoothed charge distribution is a good predictor of this behaviour. We are thus able to recommend a consistent set of parameters for the models.

We investigate the screening properties of Gaussian charge models of electrolyte solutions by analysing the asymptotic behaviour of the pair distribution functions. We use a combination of Monte-Carlo simulations with the hyper-netted chain integral equation closure, and the random phase approximation, to establish the conditions under which a screening length is well defined and the extent to which it matches the expected Debye length. For practical applications, for example in dissipative particle dynamics, we are able to summarise our results in succinct rules-of-thumb which can be used for mesoscale modeling of electrolyte solutions. We thereby establish a solid foundation for future work, such as the systematic incorporation of specific ion effects.

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The literature data bear witness to strong synergistic effects in mixed aqueous solutions of alkylamine oxides and alkyl sulfates. Physicochemical properties of these systems depend essentially on pH, which is due to protonation of amine oxide. Interplay of several types of intermolecular interactions including chemical ones results in complex phase diagrams. New experimental data presented in the paper refer to the solid−liquid equilibrium (the Krafft boundary), the composition of crystallizing complexes, and the critical micelle concentration (cmc) in mixed aqueous solutions containing dimethyldodecylamine oxide and sodium or magnesium dodecyl sulfate. The temperature maximum suggesting the formation of a 1:1 amine oxide−dodecyl sulfate complex is observed at the curves of dissolution temperature versus surfactant-based composition; the shape of the curves indicates that complexes of other stoichiometries can be formed in solutions enriched with amine oxide. The dissolution temperature for the 1:1 mixture (and correspondingly, the concentration of the complex in the solution) grows with growing acidity. In both systems under study, the dissolution temperature becomes 48 °C at a pH of about 5 and does not change on further pH lowering. Chemical analysis has shown that the solid phase precipitated from basic solutions contains metal ions whereas at pH ≤ 5 the complex between the protonated amine oxide and dodecyl sulfate anion is crystallized. The cmc value for 1:1 acidic mixtures does not depend on the cation nature and is 2 orders of magnitude lower than that for solutions at the natural pH (which are slightly basic). The pseudophase model taking into account the reactions of amine oxide protonation and 1:1 complex formation reproduces satisfactorily the pH effect on the solubility diagrams in the dimethyldodecylamine oxide−sodium dodecyl sulfate−water system.

We report the temporal stability of the dispersion of single-wall carbon nanotubes in a binary solvent “water + glycerol” having eutectic composition (ca. 67% wt.) with sodium dodecylbenzene sulfonate as a dispersant. The system procures good temporal and thermal stability: its absorption spectra demonstrate no changes during one-year storage with temperature spanning −40 to +40 °C. The system provides non-linear optical power limiting of the incident laser radiation (532 nm) in a one-shot and pulse-periodic regimes of its applying.