Thesis (M.S.)--University of Wisconsin--Madison, 1976. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 83-85).

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Thesis (M.S.)--Missouri University of Science and Technology, 2010. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 8, 2010) Includes bibliographical references (p. 59-60).

The major challenge of the research was to characterize and develop concepts for establishing structure/property relationships between the functionality of the polymer backbone, the states of water and the membrane transport properties. Most of the hydrocarbon based random copolymers reported in the literature show reduced proton conductivity at low water content. This was attributed to the formation of an isolated morphology. Over the last few years our group has synthesized thermally stable multiblock copolymers with varying chemical structures and compositions. Block copolymers consist of two or more incompatible polymers (i.e. blocks) that are chemically conjoined in the same chain. The transport properties of the multiblock copolymers showed a strong dependence on the morphology in contrast to the random copolymers. Irrespective of the nature of the backbone, the transport properties scaled with the block lengths of the copolymers. An increase in block length for a given series of block copolymer was associated with improved proton conduction, particularly under partially hydrated conditions compared to the random copolymers. The structure-property relationship of the proton conductivity and self-diffusion coefficient of water was obtained as a function of the volume fraction of water for all the random and block copolymers. At a given volume fraction, the block copolymers displayed both higher self-diffusion coefficients of water and proton conductivities relative to the random copolymers. This improvement in transport properties indicates the presence of desired and favorable morphology for the blocks. For DMFC applications, the block copolymers also showed low methanol permeability and high selectivity. The states of water in the copolymers were characterized using DSC and NMR relaxation techniques. At similar ionic contents, the free water concentration increased with increasing block lengths. The distribution of the states of water in the copolymers correlates to transport properties. This knowledge, coupled with the state of water experiments, transport measurements, and chemical structure of the copolymers provided a fundamental picture of how the chemical nature of a phase separated copolymer influences its transport properties. The experimental procedure involved impedance spectroscopy, DSC, TGA, FTIR, DMA, pulse gradient stimulated echo (PGSE) NMR, NMR relaxation experiments and various electrochemical fuel cell performance experiments. / Ph. D.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-04-27T12:47:11Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese Doutorado - Bruno Silva Leite.pdf: 6944857 bytes, checksum: 10fdad3c0d495f51166d24686d966b92 (MD5) / Made available in DSpace on 2017-04-27T12:47:11Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese Doutorado - Bruno Silva Leite.pdf: 6944857 bytes, checksum: 10fdad3c0d495f51166d24686d966b92 (MD5) Previous issue date: 2016-12-16 / Um refinamento na análise do espectro de absorção IV das manchas solares permitiu a identificação de 67 novas bandas, que agora se somam as 185 já identificadas como transições rotovibracionais da molécula de água. Os resultados revelam transições dentro do mesmo nível vibracional assim como transições cruzadas envolvendo níveis vibracionais distintos. Identificamos ainda bandas que podem ser atribuídas aos estados eletrônicos excitados1ue 3 u, ambos com geometria linear D∞h. A partir desta identificação, consideramos também a possível ocorrência de outros estados excitados da molécula de água nas manchas solares, como os estados paramagnéticos 3A2 e 3B2. Os estados eletrônicos da molécula de água foram calculados em nível B3LYP/AUG-cc-pVTZ, obtendo-se geometria de equilíbrio, momentos de dipolo elétrico e magnético e outras propriedades que foram empregados para discutir a influência de estados eletrônicos excitados na dinâmica das manchas solares e no aumento de seu campo magnético. / A refinement in the analysis of the infrared absorption spectra of the sunspots allowed the identification of 67 new bands, which now add up to the 185 already identified as rotovibrational transitions of the water molecule. The results reveal transitions within the same vibrational level as well as cross transitions involving different vibrational levels. We have also identified bands that can be assigned to the excited electronic states 1uand 3u, both with linear geometry D∞h. From this identification, we also consider the possible occurrence of other excited states of the water molecule in sunspots, such as paramagnetic states 3A2 and 3B2. The electronic states of the water molecule were calculated at the B3LYP/AUG-cc-pVTZ level, obtaining equilibrium geometry, electric and magnetic dipole moments, and other properties that were used to discuss the influence of excited electronic states on the dynamics of sunspots and in the increase of their magnetic field.