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Title: Polymer-driven colloidal self-assembly
Author: Jahn, S.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2011
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In this thesis, we used an experimental approach to study the self-assembly of colloids driven by a bio- or synthetic polymer. We investigated three different systems: (1) Micrometer-sized polystyrene colloids were coated with very long phage-DNA and examined in the presence of protein-multilayers and weakly attractive poly-L-lysine poly (ethylene glycol) surfaces modified with and without short single-stranded DNA. We observed the formation of 2D crystals several micrometers above all surfaces as well as a difference in “flying height” of the crystals depending on the surface coating. Once formed, the crystals remained stable over weeks at various ionic strengths. A factor identified to play a major role in the formation of crystals is colloidal polydispersity. (2) We studied the behaviour of negatively charged, non-adsorbing, bare silica microspheres on “soft” substrates. Surface-grafted thick DNA brushes were compared to polyacrylamide hydrogels of varying rigidity. The evolution of 2D square-lattices in coexistence with hexagonally ordered structures surrounded by a dilute colloidal gas above soft surfaces was identified. This observation appears to be due to an attractive interaction based on the elastic deformation of the substrate caused by the colloids independent of the nature of the support substrate. For substrates with elastic moduli above a certain threshold, we observed no ordering. (3) We used superparamagnetic iron oxide nanoparticles grafted with thermo-responsive co-polymers of distinct molar fractions to demonstrate the reversible agglomeration in aqueous media and inside cellular microcompartments. The agglomeration led to a significant contrast enhancement in T2*-weighted MRI imaging. We developed and optimised a hypo-osmotic dilutional method to incorporate the particles into Red Blood Cells to evaluate their biocompatibility and suitability as long-circulating contrast agents and drug delivery devices.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available