Surface-modification And Property Study Of Nanoobjects

Inorganic nanoparticles are promising and valuable materials with fascinating properties such as optical, magnetic and electronic properties. But the exploitation requires the particles to be dispersed homogeneously. The best way to avoid aggregation is to graft polymer chains onto the particles covalently, forming organic-inorganic hybrid materials. Those hybrid materials composed of inorganic core and organic polymer shell have intrigued interest for the combination of the properties of both the inorganic particles and the polymer such as solubility, compatibility and easy processing. Hybrid nanoparticles’self-assembly at the water-oil interface promises its application in the field of capsulation, controllable release and porous materials. Reversible addition fragmentation chain transfer mediated polymerization (RAFT), one of living radical polymerization techniques, has attracted considerable interest. It provides molecular weights predetermined by the chain transfer agent and conversion, and, more importantly, produces polymers under mild reaction conditions. The main purpose of this work is to study the synthesis of well-defined functional polymers via the RAFT process and surface-modification as well as the self-assembly behavior of nanobjects with polymers resulting from RAFT polymerization. This dissertation contains the following aspects:A series of amphiphilic polymer grafted silica nanoparticles have been prepared and the self-assembly of which is studied. Triblock copolymers PMMA-6-PGMA-6-P/BMA containing small amount of epoxy groups in the middle of the chains were synthesized by sequential polymerization of functional monomers using macro-chain transfer agent via RAFT process. The triblock copolymers were grafted onto silica nanoparticles by the reaction of epoxy groups in the block copolymers of PMMA-6-PGMA-6-P/BMA and silanol group on the surface of silica nanoparticles. This "center-linking" process resulting in "V shaped" block polymer functionalized silica nanoparticles PMMA-g-NSiO2-g-PfBMA. TEM, SEM, IR, NMR and TGA were employed to determine the structure, morphology, and the grafting quantities of the resulting products. Amphiphilic polymers grafted silica nanoparticles PMMA-g- NSiCh-g-PMAA was prepared by subsequent hydrolysis of the/er/-butyl group into carboxylic group. Those "V shaped" amphiphilic polymer grafted silica nanoparticles displayed good dispersibility not only in organic solvent but also in water. PMMA-g-NSio2-g-PMAA could self-assemble at the interfaces of chloroform and water, or toluene and water. The type and characters of the emulsion could be changed by changing the wettability of the copolymer, the concentration of the grafted particles and the pH of aqueous dispersion.Amphiphilic polymer grafted silica nanoparticles, Y(OH)3 nanotubes and ZnAl-LDH have been prepared and the self-assembly of which is studied. The triblock copolymers PMMA-b-PGMA-b-P/BMA were grafted onto silica nanoparticles, Y(OH)3 nanotubes and ZnAl-LDH by the reaction of epoxy groups in the block copolymers of PMMA-b-PGMA-b-P/BMA and hydroxyl groups on the surface of nanoobjects. Amphiphilic polymers-grafted nanoobjects were prepared by subsequent hydrolysis of the tert-butyl group into carboxylic group.Those "V shaped" amphiphilic polymer grafted nanoobjects displayed dispersibility not only in organic solvent but also in water. Grafted nanoobjects could self-assemble at the interfaces of chloroform and water, or toluene and water. A mixture of two or three of them could also self-assemble at the water-oil interfaces. SEM was employed to determine the micromorphology of the film.