Molecular Dynamics Simulation And DFT Calculation For Electrospinning Process Of Polysulfone Aems

Alkaline anion-exchange membrane fuel cells(AAEMFCs)have attracted worldwide interest due to their advantages including fast oxygen reduction kinetics,high compatibility with non-precious-metal catalyst and low cost.As one of the key components in AAEMFCs,the performance of alkaline anion exchange membranes(AAEMs)directly affects the power output and durability of the fuel cells.When fuel cell operating,the ideal anion exchange membrane should have good hydroxide ion transmission rate,alkali stability and mechanical properties.The hydrophilic-hydrophobic microphase separation structure of the polymer electrolyte membrane is designed so that hydrophilic functional groups are aggregated to form ion clusters,and OH~-ions are transferred.The hydrophobic polymer main chain is aggregated to provide membrane mechanical strength,which can significantly improve membrane performance.Electrospinning is an effective method to regulate the microphase separation structure of membranes,but its mechanism has not yet been clarified.In this work,molecular dynamics simulation(MD)and density functional theory(DFT)calculations are used to study the imidazole-functionalized polysulfone(IMPsf)and dimethylformamide(DMF)systems during electrospinning.Mechanism of electrospinning to control microphase separation structure of membrane.First,molecular dynamics simulation was used to calculate the interaction relationship of components in the IMPsf-DMF solution.The radial distribution function was calculated and it was found that due to the bridging effect of Cl~-,imidazoles in the solution would aggregate to form ion clusters.In addition,DMF forms a hydrogen bond with the imidazole functional group through O atom.Under electrospinning conditions,this effect is enhanced,and the functional group attracts more DMF,resulting in a weaker Cl~-bridge effect.Combined with the literature,it is speculated that ion cluster formation is related to DMF.Then,the change of a single IMPsf and DMF in the electric field is studied.Through DFT calculations,it is found that for DMF,the negative charge is concentrated on the O atom and the positive charge is concentrated on the C atom.Under the action of the electric field,the dipole moment of the DMF increases.In the casting condition,the DMF dipole moment is4.22 D,while in the 0.15 V/?electric field,the DMF dipole moment is 4.77 D.Under casting conditions,the imidazole group will form a?-?conjugation with the main chain,thereby inhibiting the separation of the hydrophilic imidazole group from the hydrophobic main chain.Under electrospinning conditions,the DMF dipole moment increases,on the one hand,the DMF self-diffusion coefficient decreases,and the kinetic energy of the solvent is more difficult to overcome the interaction between the solvent and the polymer,and the solvent can better drag the group to move outward.On the other hand,the binding ability of DMF and the imidazole group is enhanced,which makes it possible to overcome the?-?conjugation between the imidazole and the main chain during electrospinning.,To better achieve hydrophilic and hydrophobic microphase separation.Finally,by analyzing the DFT calculation results of QAPsf,the performance of QAPsf prepared by electrospinning was predicted,and the simulation was inferred that the effect of electrospinning on the QAPSf conductivity would be less than that of IMPsf,and it was verified through comparison of literature data.