Fabrication Of Composite Micro- And Nanostructures At The Liquid/liquid Interface

Amphiphilic block copolymers exhibit abundant self-assembly behavior at liquid/liquid interfaces. The microstructures formed in the film vary with the polymer structure. The molecular structure of polymer and the concentration of inorganic species had a large effect on the adsorption and self-assembly of the polymers and on the final microstructures. In this thesis, we described some self-assembly behavior of three amphiphilic block copolymers:(1), the adsorption and self-assembly behavior of PS-b-P2VP and the effects of the total molecular weight of polymer and the concentrations of the inorganic species on the morphologies and structures of the resulting films were analyzed; (2), the adsorption and self-assembly behavior of P4VP-b-PS-b-P4VP interacted with inorganic species including AgNO3, H2PtCl6, Zn(CH3COO)2, Hg(CH3COO)2, Cd(CH3COO)2 solutions at liquid/liquid interfaces. The inorganic species had a large effect on the adsorption and self-assembly behavior of the polymers and on the final microstructure; (3), a DMF/CHCl3 solution of polystyrene-b-poly(acryl acid)-b-polystyrene (PS-b-PAA-b-PS) or PS-b-PAA-b-PS/ 1,6-diaminohexane (DAH) (lower phase) and an aqueous solution of AgNO3 (upper phase) constituted a planar liquid/liquid interface. Polymer molecules and Ag+ ions assembled into microcapsules around emulsion droplets that adsorbed at the planar liquid/liquid interface. The film formed with DAH acted as a cross-linker exhibited catalytic and thermoresponsive activity.1. The adsorption and self-assembly behavior of PS-b-P2VP at liquid/liquid interfaces.Diblock copolymers (polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP)) with different molecular weights self-assembled into various supramolecular microstructures at the polymer chloroform solution/aqueous chloroauric acid interface under different conditions. Generally, multilayered foam films composed of microcapsules with walls decorated with or without round interfacial micelles formed when using a higher concentration of aqueous solution; honeycomb monolayers appeared with decreasing aqueous solution concentration; fish net-like or labyrinthine monolayers were generated with a further decrease in aqueous concentration. The appearance of these microstructures reflects the different adsorption and self-assembling behaviors of PS-b-P2VP including interfacial micellization, encapsulation, and microphase separation under different conditions. In addition, the relative molecular weights of the two blocks and the total molecular weight of the polymers had a large effect on the adsorption and self-assembly of the polymers and on the final microstructure architecture. Furthermore, the factors that affect the adsorption rate and intermolecular interactions of the polymers and, consequentially, the self-assembling behavior and final microstructures are discussed. The catalytic activities of these composite microstructures were evaluated.2. The adsorption and self-assembly behavior of P4VP-b-PS-b-P4VP at liquid/liquid interfaces.P4VP-b-PS-b-P4VP adsorbed and interacted with inorganic species including AgNO3, H2PtCl6, Zn(CH3COO)2, Hg(CH3COO)2, Cd(CH3COO)2 solutions and formed composite films at liquid/liquid interfaces. Transmission electron microscopic observations confirmed that different microstructures formed in the films including spherical nanoarray, foam-like structures, parallel and spiral nanowires. The appearance of these microstructures reflects the inorganic species have an effect on the morphologies and structures of the resulting films. This was ascribed to the differences of the strength and mode of interaction between polymer and inorganic species. X-ray photoelectron spectroscopic investigations revealed the composition of composite films. The films doped with Ag or Pt exhibited high catalytic activity for hydrogenation of nitro compounds. X-ray photoelectron spectrum and UV-vis showed the films containing Zn2+, Cd2+ or Hg2+ generated sulfide nanoclusters after treatment of H2S.3. Emulsion-directed adsorption and assembly fabrication of thermosensitive composite films at the planar liquid/liquid interface.An aqueous solution of AgNO3 (upper phase) and a DMF/CHCl3 solution of polystyrene-b-poly(acryl acid)-b-polystyrene (PS-b-PAA-b-PS) or PS-b-PAA-b-PS/ 1,6-diaminohexane (DAH) (lower phase) constituted a planar liquid/liquid interface. The lower phase gradually transformed to a water-in-oil (W/O) emulsion via spontaneous emulsification due to the "ouzo effect". Polymer molecules, DAH molecules, and Ag+ ions assembled into microcapsules around emulsion droplets that adsorbed at the planar liquid/liquid interface, resulting in formation of a foam film. DAH acted as a cross-linker during this process. Transmission electron microscopic observations indicated that Ag nanoclusters that were generated through reduction of Ag+ ions by DMF were homogeneously dispersed in the walls of the foam structure. X-ray photoelectron spectroscopic investigations revealed that Ag(â… ) and Ag(0) coexisted in the film, and Ag(â… ) transformed to Ag(0) after further treatment. The film formed without DAH was not stable, while the film formed with DAH was very stable due to intermolecular attraction between PAA and DAH and formation of amides, as revealed by FTIR spectra. The film formed with DAH exhibited high and durable catalytic activity for hydrogenation of nitro compounds and, very interestingly, exhibited thermoresponsive catalytic behavior.