Multiple morphologies of self-assembled aggregates of polystyrene- b-poly(ethylene oxide) (PS-b-PEO) diblock copolymers in dilute solution have been studied. The PS blocks are relatively long compared to the PEO blocks. The aggregates are prepared by the addition of water or methanol to the copolymer solutions in N,N-dimethylformamide (DMF), dioxane, or tetrahydrofuran (THF) to induce the aggregation of the PS blocks. Aqueous solutions of the aggregates are obtained by dialysis with water. Morphologies are directly studied by transmission electron microscopy (TEM). / The morphogenic effect of the copolymer composition indicates that as the EO content in the diblock decreases, the morphology of the self-assembled aggregates changes progressively through spheres, rods, bilayers, and ultimately to inverted aggregates. The observed bilayers include lamellae, vesicles, tubules and large compound vesicles (LCVs), and the inverted aggregates include inverted (hollow) hoops with a hexagonal array and large compound micelles (LCMs). / The morphological transition from vesicles to inverted hoops is investigated, and a three-step mechanism is proposed. This mechanism involves a thickening of the vesicle walls accompanied by the formation of the hollow rods in the walls, and a decrease in the size of the original water core. Possible mechanisms of the formation of large vesicles from lamellae, as well as tubules and LCVs from vesicles are discussed. / The formation of the self-assembled aggregates with various morphologies is believed to be mainly controlled by the balance of three interactions arising from the core, the corona, and the core-solvent interface. Any factors, such as the addition of salt, which affect the balance will cause morphological changes. Accordingly, the morphogenic effects of added electrolytes, temperature, the common solvent, and the precipitant are studied. The study shows that various morphologies can be prepared from one diblock copolymer.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.36076 |
| Date | January 1998 |
| Creators | Yu, Kui, 1967- |
| Contributors | Eisenberg, Adi (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001687383, proquestno: NQ56703, Theses scanned by UMI/ProQuest. |
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