|M.Sc Student||Sokol Edith|
|Subject||Synthesis of Metal-Oxide Nanoclusters/Polystyrene Ionomer|
Composites and Their Interfacial Characterization
|Department||Department of Chemical Engineering||Supervisor||Ms. Rina Tannenbaum|
|Full Thesis text|
Some of the most studied composite systems in the last few decades have been the organic/inorganic hybrid nanocomposites. These systems, based upon the incorporation of clusters (or nanoparticles) of metals or metal oxides into a polymeric matrix, offer the possibility of superior mechanical properties, mainly controlled by the nature of the load-transfer through the polymer-particle interface. In this research, the interface properties were changed by controlled electrostatic interactions between sulfonated-polystyrene ionomers and iron oxide nanoparticles. The ionomers were synthesized by a newly-developed "one-pot" synthesis, enabling strict control over ionization extent, while reaching extremely high sulfonation efficiencies. The iron oxide nanoparticles were synthesized in the presence of the different ionomers, by a thermal decomposition technique, resulting in self-assembled clusters, composed of 2-5 nm iron oxide particles, uniform in size. The self-assembled supramolecular structures range from 30nm to 500nm in diameter, depending on the degree of sulfonation of the ionomer. Such structures result from the balance between attractive electrostatic interactions between polymer and particle, and the repulsive forces induced by the ionic groups along the backbone of the polymer. These results fit well with a theoretical model, predicting the dependency of the number of anchoring points of the polymeric chain onto the particle, with the changes in the chemical nature of polymer-particle surface-linkage. Mechanical properties analysis (by nanoindentation) of these nanocomposites showed a tradeoff between the rigidity of the polymer due to the presence of the sulfonic acid groups and the extent of reinforcement resulting from the ionic interaction between the polymer and the particles' surface. These hybrid composites demonstrate the possibility of controlling the macro-properties of the composite by pre-designing the interfacial properties in the nano-scale.