The performances of Proton Exchange Membrane Fuel Cells (PEMFCs) are strongly influenced by the proton conductivity of the solid electrolyte. The azole-based polymers are among the most promising materials to improve the effectiveness of these systems. A theoretical study of proton transfer (PT) reaction in protonated imidazole, 1,2,3-triazole, and tetrazole dimers has been performed. The developed DFT protocol has been applied on more complex systems. The results obtained from the investigation performed on Poly(4-vinyl-imidazole) (P4VI) suggest that the commonly accepted (Grotthuss) conduction mechanism, based on a sequential proton transfer between imidazole moieties, could be impeded in this system because of the backbone constraint. Such a study, performed through a combined Density Functional Theory (DFT) / Molecular Dynamics simulations (MD) approach, allowed to hypothesize an alternative mechanism of conduction. A further study performed on phosphoric-acid (H3PO4) included models has revealed as low concentrations of H3PO4 could allow for the Grotthuss mechanism despite the polymeric constraint. The underpinning role played by the backbone topology on the conductivity has been then confirmed by the investigation carried out on a second polymer: the wire tethering position can strongly affect the mechanism of conduction. In short, the obtained simulations show how the polymeric matrix play a crucial role in the conductivity mechanism. The present research represents a first effort for a more systematic study of the relationship between backbone connectivity and efficiency of the charge transport
