Specifics of solvation of sulfonated polyelectrolytes in water, dimethylmethylphosphonate, and their mixture: A molecular simulation study

Abstract

Sulfonated polyelectrolyte membranes (PEMs), such as Nafion and styrene-olefin block copolymers, are explored as permselective membranes for fuel cells as well as suitable barrier materials against chemical agents. The permselective properties of PEM are determined by their microphase segregation into hydrophilic and hydrophobic domains. We performed classical molecular dynamics simulations of solvation of the hydrophilic fragments of PEM exemplified on sulfonated polystyrene (sPS) with potassium, calcium, and aluminum as counterions, in water, phosphor-organic nerve agent simulant dimethylmethylphosphonate (DMMP), and their binary mixture. The force field for the sulfonate group has been developed by optimizing the potential parameters to fit the benzenesulfonate conformations obtained from the density functional theory. For a comparison, we considered perfluorosulfonate oligomers representing fragments of Nafion polymer. We found a noticeable difference between the geometries of the polymer backbone in different solvents. The polymer backbone is stiffer in DMMP for both sPS and Nafion. An anisotropic structuring of the solvent around the phenylsulfonate group is substantially stronger than around the Nafion sidechain due to the rigidity and the anisotropy of the phenylsulfonate group. The counterion significantly affects the conformations of solvated sPS: the rigidity of the backbone increases when potassium or calcium ions are replaced by trivalent aluminum ions.

Coarse-grained simulations of polyelectrolyte complexes: MARTINI models for poly(styrene sulfonate) and poly(diallyldimethylammonium)

“…4, the atomistic OPLS/AA force field parameters for PSS have been adopted from Ref. 3 and for PDADMA building blocks from Ref. 2.…”

Coarse-grained model of water diffusion and proton conductivity in hydrated polyelectrolyte membrane

“…The segregation inside hydrated sPS was observed both experimentally and in atomistic simulations. [58][59][60] The morphology is irregular and depends on the level of sulfonation, and the scale of segregation is believed to be relatively small. Small size of hydrophilic channels, tangible dissociation constant of the acid group, and ability to vary the sulfonation level substantially make sPS an ideal system for examining the advantages and limitations of our DPD approach.…”

Solvent effects of 1-ethyl-3-methylimidazolium acetate: solvation and dynamic behavior of polar and apolar solutes

“…49 Indeed, promising approaches towards the full understanding of solvent behavior for macromolecular properties have been recently published. [50][51][52] However, it has to be stated that only a few aspects of solvophilic and solvophobic solvation properties are in general known. [53][54][55] The study of the IL solvent behavior is therefore a challenging task with often unexpected outcomes.…”