Solid-state NMR Investigations of Proton Conducting Membranes

This thesis applies magnetic resonance techniques to novel and traditional proton conductingmaterials in order to gain a better understanding of the molecular aspects of theirperformance. An array of experiments and techniques are used. One material is a morphologicallydesigned block copolymer/ionic liquid system. Simple 1-D variable temperature(VT) 1H magic angle spinning (MAS) NMR is used to catalogue the dynamic chemicalshifts, which relates to the prevalence of hydrogen bonding. Relaxation data are usedto measure the relative mobilities of conduction protons, and these data are related topolymer physics phenomena. The effect of morphology is investigated by comparing blockcopolymer data to a series of homopolymer analogues with no morphological structure.The role of entropy in these systems is discussed as well as the effect of a non-symmetricionic liquids.NMR techniques were also applied to more traditional materials, namely perfluorosulfonicacid membranes modified with amphoteric imidazole compounds. The chemicalenvironments of the imidazole as well as the dynamics of proton transfer are measuredwith Solid-state 1H NMR. The effect of imidazole concentration is also considered. 1H-13C cross polarization (CP) MAS NMR is used to reveal the presence of both fast andslow moving imidazole in the membranes. Pulsed field gradient (PFG) NMR is used toquantify the diffusion of protons and methanol through the material.The goal of replacing gaseous hydrogen with organic virtual carrier molecules as aproton source for proton exchange membranes (PEM) fuel cells is investigate by testingthe effect of model organic liquids in contact with typical membrane materials. A suiteof data, including 19F NMR relaxation data of the polymer backbone and sidechains, areused to explain bulk phenomena and membrane performance