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Title: Diffusion of macromolecules in confined environments
Author: Mears, Matthew
ISNI:       0000 0004 2718 783X
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2011
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This thesis is concerned with using diffusing molecules as a probe to understanding changes in both two- and three-dimensional polymer systems. Fluorescence correlation spectroscopy (FCS) is used to measure the diffusion coefficient of a fluorescently labelled molecule within poly (methacrylic acid) (PMAA hydrogels and adsorbed onto poly(alkyl mcthacrylate) thin films. Responsive hydrogels such as PMAA arc of great importance in controlled release systems such as drug delivery. The hydrogcls studied were found to respond to temperature, pH. and salt concentrations in ways that can be utilised for producing systems that change in predetermined ways under controlled conditions. Thin polymer films. both homopolymer and polymer blends are found to exhibit a transition process between glass and liquid states. Existing theories present the transition as a sharp. almost instantaneous process but FCS and ellipsometric measurements find this to be an insufficient model. Not only is the glass transition found to occur over a temperature range but the diffusion of adsorbed molecule and the measured friction coefficient. Are found to increase dralllatically at the transition temperature range after which they are similar to the values below the transition. Furthermore polymer blends (Ire found to exhibit two distinct transitions. each with an increase in adsorbed diffusion that are unexpected in the existing theoretical understanding of polymer blends.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available