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Amphiphilic block and graft copolymers have been studied because of the possibility of tailoring their complex and fascinating chemical properties. Potential applications include wetting agents, foaming agents, plastic modifiers as well as biomedical applications in drug delivery, owing to their biocompatible and low toxic nature. This thesis describes the study of a series of amphiphilic block copolymers, known as Pluronics, and their aqueous interaction with a hydrophobic drug, flurbiprofen. Synthesis and characterisation of novel graft copolymers with interesting associative behaviour that is less influenced by concentration is also another major aspect of the work described in this thesis. Pulsed-field gradient stimulated-echo nuclear magnetic resonance (pFGSE- NMR) and surface tension measurements have been used to show that the addition of flurbiprofen promotes micellisation of Pluronic triblock copolymers (PI03, P123, and L43). Structural changes in the micelles ofPluronics PI03 and P123, as a function of temperature, eo-solvent (ethanol, 10 wt/vol %), and the addition of the hydrophobic drug flurbiprofen were also investigated by small- angle neutron scattering (SANS). Flurbiprofen was shown to be released from micelles by increasing the solution pH. At higher pH, the drug is ionised and the fraction of polymer in micelles reduces. Synthesis of novel graft copolymers was carried out using a "grafting onto" method. In this approach, the functional group of a hydrophobic backbone will react with the functional group of the copolymer chains. The graft copolymers composed of either hydrophilic Pluronics or sulfonated poly(ethylene oxide) chains and hydrophobic backbones, displayed formation of core-shell micelles in selective solvents. The Pluronic graft copolymers showed the potential for solubilising hydrophobic drug molecules in aqueous solution even at low polymer concentrations. These graft copolymers and their interactions with flurbiprofen were characterised by PFGSE-NMR and SANS.

Amphiphilic block copolymers self-assemble in water to form discrete aggregates of different morphologies so as to minimize the interaction of the hydrophobic moiety with the surrounding aqueous medium. The most commonly observed morphologies are spherical micelles, cylindrical micelles and vesicles; however, more complex morphologies such as disk-like micelles, toroids and internally-structured nanospheres are becoming more frequently observed and targeted in synthesis. The type of morphology formed is fundamentally dependent upon the block copolymer composition and structure, and so the synthesis of well-defined block copolymers is a necessity for the production of designer nanoparticles. To this end, controlledl"living" polymerization techniques are utilized to yield block copolymers with well-defined structure and functionality, and the synthesis of stimuli-responsive block copolymers allows for the formation of smart aggregates. This work presents the formation of nanospheres with complex internal structure from semi-crystalline amphiphilic block copolymers of poly( ethylene oxide) and poly( octadecyl methacrylate). The block copolymers were synthesized using atom transfer radical polymerization (ATRP) to enable control over the relative compositions and molecular weight. Aqueous dispersions of the block copolymers yielded complex polymer cubosomes: nanospheres with internal bicontinuous morphology. The internal structure was investigated and characterized using microscopy techniques and the. effects of block composition and preparation conditions on the morphology were investigated. The nanospheres exhibited temperature-responsive behaviour which stemmed from the hydrophobic PODMA block. The internal structure and thermal behaviour of these aggregates provide the possibility of their application as a temperature-controlled delivery system.

In this thesis the protein resistive nature of polyethylene oxide brushes shall be investigated. Initially a novel grafting-to procedure for the production of high molecular weight and high grafting density PEO brushes will be presented. This procedure will allow the accurate control of the grafting density of PEO brushes. The crystallisation and oxidation of PEO brushes is also briefly investigated. Ex situ ellipsometry experiments will show that the adsorbed amount of protein is related to the surface coverage of polymer. supporting the random sequential adsorption theory (RSA-model) of Katira et al. However. through in situ QCM-D experiments it will be shown that RSA-model cannot fully describe the protein adsorption kinetics and may need to be revised to take these observations into account. We will show through use of an exponential model that the adsorption of protein at PEO brushes is a site blocking process and not an entropic process on the time scales measured here. Neutron reflectivity experiments on the INTER reflectometer instrument at ISIS show that the lysozyme protein is most likely adsorbing in the primary position at the gold- brush interface. The experiments presented in this thesis support the conclusion that the protein resistive nature of PEO brushes is that of a site blocking barrier.