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Title: Dynamics of interfaces in surfactant lamellar phases
Author: Buchanan, Mark
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2000
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The hydrophilic and hydrophobic properties of surfactant molecules enable them to organise in large structures when dissolved in water. Under certain conditions they can organise in bilayers forming the lamellar phase. The equilibrium properties of this phase have been well studied. In this study we observe the dynamic and kinetic behaviour during the swelling and dissolution of the lamellar phase. We have performed penetration scan experiments under different thermodynamic conditions using video microscopy. When the lamellar phase is insoluble in water classic myelin instabilities are observed. These instabilities have been studied with microscopy and in some cases we use tracer particles to follow fluid flow in between the myelins. We report qualitative features of the myelin growth as well as provide some quantification of the swelling process. Specifically, we determine an effective diffusion coefficient for the swelling lamellar phase. In the case of a soluble lamellar phase myelin instabilities are not observed. Also, we report instabilities observed at the liquid surfactant/lamellar interface. These instabilities appear to create multilayer vesicles which move into the liquid surfactant. We have found these to be attached to the surface of a wedge of lamellar phase that moves along the surface of the cell into the liquid surfactant phase. Also, we have conducted contact experiments using a presheared lamellar phase the so called “onion” texture. The onion phase does not form myelins as in the normal case. Instead the onions dissolve into an isotropic (“sponge”) phase. During the onion dissolution a small stable core remains. If the sample is observed over a more extended period the onions are observed to coalesce. These features were investigated at different temperatures.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available