The Morphology Control Of Hybrid Nanomaterials From Self-assembly Of Block Copolymers

The self-assembly of block copolymers (BCP) play an important role in nanomaterials and nanotechnology. But how to design a simple, high-efficiency and low-cost routes to gain different nanostructure, which can meet different needs, is still remaining a significant challenge. In this dissertation, we investigated the self-assembly of amphiphilic block copolymers in selective dilute solution. By using the micelles of BCP as templates, which can co-assemble with the inorganic precursors, different nanostructures can be obtained. In addition, the block copolymer micelles on the response of the temperature and pressure, and the morphological change of block copolymer/SG , in the presence of supercritical fluid carbon dioxide, were also discussed. Three main experimental researches are included as follow:(1) The self-assembly of polystyrene-b-poly(2-vinylpyridine)/HAuCl₄ (PS-b-P2VP/HAuCl₄) complexes in solutions is described. A morphological change from spheres to aggregated spheres, and then to vesicles, all of which contain Au precursor within the micellar corona or vesicle shell, can be prepared from an identical diblock copolymer by controlling the solvent selectivity. If the volume ratio (VR) of ethanol/THF is 0.1, no micelles are formed. When the VR reaches 0.25, spherical micelles are formed. When the VR of ethanol/THF is in the range of 0.3⁰.7, aggregated spheres are formed. When the VR is increased to 1.0, a transition from aggregated spheres to vesicles was observed. The possible mechanisms leading to the morphological transitions are also discussed. This may be a simple, facile route for preparation of a desired gold-containing aggregate.(2) A novel route for a preparation of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer vesicles induced by scCO₂ is demonstrated. When PS-b-PEO block copolymer solutions in tetrahydrofuran (THF) are treated with scCO₂ at 70 oC for different times, PS-b-PEO copolymers first assemble into aggregated spheres; then aggregated spheres change into large compound micelles and finally evolve into vesicles. And block copolymer/SG in supercritical carbon dioxide has also formed vesicles. The possible formation mechanism of the vesicles is discussed. This method may be used to prepare hydrophobic drug-loaded vesicles in future.(3) The co-assemble of block copolymer poly(2-vinylpyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) and HAuCl₄ in toluene is disscused. By adjusting the solution temperature, the annealing temperature and time, Janus particles can be achieved. P2VP-b-PEO and HAuCl₄ in toluene can form spherical micelles at 30℃to 40℃. If the annealing temperture reach to 60℃, the micellar morphology changes into Janus particles because the temperature has a great influnce on the mobility of PEO chains.