Proton diffusion in polyelectrolytes based on hydrogenated polynorbornenes with imide side groups in the repeat unit as determined by NMR and impedance spectroscopies

► Rigidity of chains constrains segregation between hydrophilic and hydrophobic moieties. ► Formation of percolation paths to facilitate proton transport is hindered. ► Proton transport in SPPhHNDI membranes occurs by vehicular type mechanism. ► Sodium ions are distributed in populations of isolated and cluster ions.