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Title: Charged surface interactions in solutions of dielectric macromolecules
Author: Croze, Ottavio
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2004
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Using a simple mean field model, we have explored how the interactions between charged surfaces are modified when they interact across an electrolytic solution of dielectric spheres, considering these must electrostatically couple to the surfaces. The coupling arises from the intra-surface electric fields, which polarise low permittivity species (oil) dissolved in a high permittivity solvent (water). The model, which already predicts a reduction of surface forces due to the spheres, was extended to describe, more realistically, “dielectric polymers” between surfaces and account for the possibility of depletion. In this case, our results indicate that an account of the coupling between charged surfaces and the polymers modifies both the polymer depletion, the electrostatics and the surfaces forces which result from them. Building on these results, it was possible to adapt a description accounting for coupling to predict phase behaviour of polymer doped smectics. This was contrasted to one which ignores the coupling, as is often assumed in the literature (though some researchers have pointed out the potential effect that polymers could have on the electrostatics of lamellar phases). Our phase diagrams predict that a neglect of coupling is not always a good approximation: particular experimental conditions will lead to qualitatively different phase behaviour between coupled and uncoupled approaches. No consistent investigation of the electrostatic effects just described has been carried out to the best of our knowledge. Since the theory we have developed applies generally to any situation where neutral polymer-like solutes are described in the vicinity of charged surfaces, the relevance of our findings to other interesting experimental situations will be discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available