Anion Coarse-Graining

Compared with coarse-grained materials, nano-particles can possess unique electronic, magnetic and optical properties. The main principle of producing nano-particles with microemulsions consists in mixing two types of microemulsions, i.e. o/w and w/o microemulsions. In this way, for example, ultra-fine particles are obtained, whose core and external shells consist of Fe salts, and in the intermediate layer copper is contained. To produce microemulsions, anionic surfactants such as Aerosol OT (AOT) are used, one mole of which can solubilise up to 8 moles of the aqueous phase. 

Ben-Naim A (2006) Molecular theory of solutions. Oxford University Press, New York Ganguly P, Schravendijk P, Hess B, van der Vegt NFA (2011) Ion pairing in aqueous electrolyte solutions with biologically relevant anions. J. Phys. Chem. B 115 3734—3739 Voth GA (ed) (2009) Coarse-graining of condensed phase and biomolecular systems. CRC Press, Boca Raton... 

Figure 22 Coarse-graining strategy used to reduce the number of interaction sites required to model an ionic liquid. In (a) the cation is represented with four sites A, B, C, and E, while the anion is represented with a single site D. In (b) the simplified coarsegrained model is depicted with associated site charges. (From Ref. 128 and used with permission.)...

Figure 23 One snapshot of a coarse-grained representation of [C4mim] [NO3] with 1000 ion pairs at T = 700 K with (a) all atoms, (b) tail groups only, (c) head groups only, and (d) anions only. Notice the tail groups organize into domains. (From Ref. 129 and used with permission.)...

Boundaries between atomistic and coarse-grained simulation approaches are floating. Atomistic simulations of ionomer systems typically employ all-atom representations of water molecules, anionic head groups, and protons. For the remaining components, the use of a coarse-grained or united-atom representation for the CF , groups in both the fluorocarbon backbone and the sidechains could markedly improve the computational efficiency of atomistic simulations. United-atom force fields permit simulations of substantially larger systems compared to all-atom force fields. For instance, Urata et al. (2005) have employed a united-atom representation of CF , ... 

Free hydrated protons produced by acid dissociation move inside of porous domains, relative to the interfacial layer of anionic surface groups. Self-consistent theories and coarse-grained molecular simulations can help to rationalize this structural picture. After demonstrating consistency with existing data on structure and transport, these modeling approaches could be employed as predictive tools in polymer design. 

Fig. 1 Coarse grain mapping for a) Polyamide 6,6, b) Polystyrene c) ionic liquid anion d) cation l-alkyle-3-methylimidazole hexaflurophosphate, mapping scheme MS2, e) mapping scheme MSI.

In a coarse grain (CG) model, called the primitive model a polyelectrolyte chain is represented by a set of hnked charged beads (Fig. 1), and the solvent is depicted as a dielectric medium. The small ions (cations and anions) are depicted as rigid spheres (Fig. 1). Each bead is spherical and has an electrical charge in its center. The number total of particles is ... 

Fig. 1 Coarse grain model for the polyelectiolyte and small ions (anion and cation)...

Fig. 4. Decoupling of persistence and exchange times for (a) cations and (b) anions in a coarse-grained model of EMf+PFe (Jeong et al., 2010).

Fig. 5. Violation of the Stokes-Einstein relation in a coarse-grained model of EMI+PF6 (Jeong et al., 2010). (a) As the temperature is lowered, Dt increases. The deviation from a constant is more substantial in case of cations. Lines are guides for the eyes, (b) The exponents in the scaling relation D are foimd to be 0.84 and 0.93 for cations and anions, respectively, while f = 1 corresjxmds to the Stokes-Einstein relation. Lines are the fitted results.

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