Preconditioning immobilized imidazole arrays for optimal proton-transfer feasibility

Classical molecular dynamics have been carried out in order to study the proton-transfer feasibility in immobilized imidazole arrays, taking into account their applications in new polymer electrolyte membrane fuel cells. The resulting trajectories have been analyzed with respect to the ability of forming hydrogen bonds, considering the angle distribution between the proton donor and acceptor groups. The dependence of the hydrogen-bond network is studied with respect to the variations of temperature, density of imidazole groups, and spacer lengths. According to the results, arrays of alkyl-imidazole molecules with three mobile CH2 groups are the most favorable to a proton-transfer reaction. Regarding the alkyl-imidazole density, no significant difference for the arrays with a spacing of 6 or 7 angstrom between the alkyl-imidazole molecules could be observed, whereas the 10 angstrom array presents a lower probability of a proton transfer. The optimal arrangement of the investigated systems is a spacing of 6 angstrom and a flexible chain length of three CH2 groups. These results confirm previous experimental and simulation analyses.