Ab initio study of cationic polymeric membranes in water and methanol

Abstract

The work is devoted to a computational study of three types of cationic polymeric membranes in Li + -ionic form, in water and methanol environments, at various solvation levels. The studied membranes Nafion, IonClad, and M3 possess the perfluorinated backbone; however, various side chains were terminated with the functional groups of distinctly different ionic strength. The paper discusses the structural features of the membrane-solvent clusters as well as an influence of the side chain nature on the dissociation of the functional groups and the binding energy of the solvent molecules. Additionally, the paper compares the obtained results for Li + -Nafion membrane in water with the results published earlier for H + and Na + forms.

Dissipative Particle Dynamics Modeling of Polyelectrolyte Membrane–Water Interfaces

“…R 0 is the mean bond length and C is the spring constant. The values of the parameters (R 0 , C, σ, γ) are chosen in accordance with previous simulation studies [11,25]…”

“…The mass of all beads is equal to unity. The DPD unit of time τ = r c (m/k B T) 0.5 corresponds to few tens of picoseconds [11,26] for a typical atomistic system. The cutoff radius r c was 0.71 nm, and the beads are propagated by using a modified Verlet integration scheme [25] with a time step ∆t = 0.05.…”

“…The parameterization used for the different PEMs in this study has also been used in the previous studies of Yamamoto et al [11] and Dorenbos [28]. Three different type of beads (A, B, and C), i.e., A:-CF 2 -CF 2 -CF 2 -CF 2 -, B:-O-CF 2 -CF(CF 3 )-O-, C:-CF 2 -CF 2 -SO 3 H have been used to construct the polyelectrolyte membranes.…”

“…Dissipative particle dynamics (DPD) is a coarse-grained simulation method used to model long-time temporal evolution and large spatial length scales. DPD simulations have been widely used to study PEMs [8][9][10][11][12][13][14][15]. Yamamoto et al [11] used DPD to analyze the phase-separated Nafion structure and found the simulated structure factors and pore radii close to the experimental values.…”

“…DPD simulations have been widely used to study PEMs [8][9][10][11][12][13][14][15]. Yamamoto et al [11] used DPD to analyze the phase-separated Nafion structure and found the simulated structure factors and pore radii close to the experimental values. Wu et al [12] simulated PEMs of different EWs and found that the water cluster radius increased with decreasing EW, and the opposite was true for the intercluster spacing.…”