Unraveling the complex hydrogen bonding of a dual-functionality proton conductor using ultrafast magic angle spinning NMR

Hydrogen bonding plays a critical role in proton-conducting polymers, as it provides the network necessary for structural (Grotthus mechanism) diffusion. This network must be both pervasive and dynamic in order for long-range proton transport to be achieved. The structural motifs must be understood, even in amorphous materials, and moreover, the lattice energies in the structure must be low enough to allow rearrangement and mobility. To this end, a novel proton-conducting candidate, 1,10-(1-H-imidazol-5yl) decanephosphonic acid and its HBr doped counterpart are considered from the molecular level as potential proton-conducting membranes. The use of high-resolution solid-state H-1 NMR to elucidate structure and dynamics of such systems is highlighted in this material. We compare our molecular-level results to macroscopic probes of proton transport in related polymers, achieved using impedance spectroscopy.