Micro-phase separation promoted by electrostatic field in electrospinning of alkaline polymer electrolytes: DFT and MD simulations

Abstract

Solution electrospinning effectively constructs long-range ionic channels in alkaline polymer electrolytes, however, the function of electrostatic field on micro-phase separation is hardly well interpreted merely through experiments. Herein, via density functional theory (DFT) and molecular dynamics (MD) simulation, it is found that non-covalent interactions among solvent-cation-backbone play important roles on ionic aggregation, and are greatly influenced by electrostatic field. During electrospinning process, the electrostatic field breaks the intramolecular π-π stacking between imidazolium cation (Im+) and benzene ring on polysulfone (PSF) backbone, contributing to Im+ aggregation. N, N-Dimethylformamide (DMF) solvent forms multiple H-bonds and π-π stacking with PSF backbone, making the PSF fold back toward the opposite direction of Im+ and promoting hydrophobic aggregation. Moreover, Im+-DMF interactions are enhanced by electrostatic fields, which weakens the interchain interactions originated from Im+-Cl− electrostatic interactions, and induces Im+ groups toward the outer layer of the nanofiber during radial evaporation of DMF, constructing continuous long-range ionic channels.