A deuterium NMR and dielectric study of glucose/water glasses

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Moran, Gerald Robert

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University of Guelph

Abstract

This thesis is an investigation of the correlation times for the molecular motion in a glucose/water glass forming system. Using separate samples containing deuterated glucose and D2O, the motions of the glucose and the water molecules in the viscous liquid and in the amorphous glass phase of glucose/water mixtures are examined. Spin-lattice relaxation measurements and spectra obtained in the solid confirm the existence of both a crystalline ice phase and an amorphous glass phase. Measurements of the DC conductivity and the NMR spectra confirm the behaviour of this system as predicted by the glucose state diagram. Diffusion measurements performed using the large gradient in the fringe field of a superconducting magnet determine the rates of translational motion of both the sugar and the water molecules over a limited range of temperature in the viscous liquid region. From the deuterium NMR spin-lattice relaxation time, T1, the spin-spin relaxation time, T2, and spin alignment measurements, correlation times for the motion of these molecules are obtained. Correlation times determined from dielectric spectroscopy are in agreement with those obtained by NMR. The correlation time for the a process increases dramatically at Tg, while the [beta]process continues into the low temperature glass phase, following an approximately Arrhenius relationship.

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Keywords

glucose/water glasses, NMR, deuterium, dielectric study, spin-lattice

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