Preparation, Functionalization And Assembly Of Polymeric Hollow Microspheres

The applications of polymer microspheres have been developed from general industry to advanced fields, including medicine, biochemistry, electronics and information, in the modern science and technologies for their unique dimension and morphology. A variety of synthetic routes have been designed to prepare polymer spheres and great progress has been made on the rescearch of the spheres size, morphology, performances and forming mechanism. Especially, hollow polymer spheres and microcapsules have attracted considerable attention owing to prominent properties of incorporation, controllable penetration and surface function, and have been found a broad range of application in the fields of medical treatment, biotechnology, chemistry and material science. With the development of inorganic/polymer material, the research on composite microspheres with unique morphologies has got ahead. At the same time, polymer spheres functionalized by the materials with fluorescence, conductivity, magnetism and catalysis have been an intriguing subject of researchers, and the formation and properties of highly ordered structures resulted from the self-assembly of functionalized composite microspheres have increasingly attractive interests. The preparation of the functionalized hybrid microspheres will broaden the application range of polymer spheres in the fields of optics, catalysis, micro-electronics and medicine, and lead developmental direction of polymer spheres in future. In Chapter two, monodisperse polymeric hollow spheres with large void were prepared via seeded emulsion polymerization in the absence of surfactant. The cavity size of the hollow spheres was tuned by changing the monomer composition, monomer/seed weight ratio and the seed size, and could be enlarged after solvent treatment. On the basis of the experimental results, the formation mechanism of the hollow spheres was discussed combined with FTIR, XPS, DSC and TGA spectra. The addition of surfactant allowed the synthesis of the hollow spheres with multi-void and solid composite spheres. In addition, the polymerization of different monomer and cross-linked agent was carried to investigate the effect of HEMA on the morphologies of polymer spheres by swelling and semicontinuous methods, and the rationality of the mechanism was proved. The method provided a favorable help for simplifying the preparation of polymeric hollow spheres.In Chapter three, rare earth complex with double bonds was added to monomer and monodisperse polymeric hollow spheres with highly fluorescence were obtained based on our preparation method. The addition amount of rare earth complex was increased by seed-swelling method. Under the conditions of a large amount of SDS, fluorescent composite spheres with perfect shape were prepared. Successively, we fabricated fluorescent colloidal crystals via single-substrate deposition using the fluorescent hollow and composite spheres as building blocks, and UV-vis spectra and fluorescent microscope were used to investigate optical properties of colloidal crystals. Furthermore, we employed SiO2/PS core-shell spheres as seeds and obtained fluorescent hollow spheres with SiO2 core by one-step seeded emulsion polymerization. As we know, many kinds of functional nanoparticles can be doped into SiO2 microspheres by sol-gel process. We believe that the method provide a platform to prepare multifunctional microspheres.In Chapter four, we demonstrated an encapsulation of rare earth complex into poly(methylmethacrylate) (PMMA) nanocapsules via a facile internal phase separation. The resulting nanocapsules gave bright red emission and possessed stable fluorescence properties. The fluorescence intensity of the nanocapsules presents different change tendency with the concentration of the two emulsifiers. Compared with bare Eu3+ complex, the nanocapsules were afforded an excellent pH-independent fluorescence. Furthermore, the average nanocapsule size was tunable with the changes in the concentration and the addition mode of the emulsifiers. Thanks to excellent biocompatibility of PMMA, the fluorescent nanocapsules will find applications in the biomedical field such as biology labeling and controlled release of drug.In Chapter five, we describe a preparation of multifunctional microspheres with fluorescence, magnetism and temperature-responsive by in-situ formation of Fe3O4 nanoparticles on polymer spheres with temperature-responsive shell, and followed by the adsorption of CdTe nanocrystals. Firstly, two-step emulsion polymerization was carried to synthesize temperature-responsive PS/PNIPAM core-shell microspheres with the positive surface. By the coprecipitation of Fe2+ and Fe3+ on the core-shell microspheres with the surface of different charge density in the presence of a certain concentration of NH3·H2O, Fe3O4/polymer hybrid spheres were obtained. On the other hand, it was attempted that the direct adsorption of the preformed Fe3O4 nanoparticels and the microspherse, but the resulting spheres were aggregated. Further, CdTe nanocrystals were adsorbed to the magnetic spheres via electrostatic interaction and physical encapsulation. We believe that the method provide a useful reference for the preparation of composite spheres with other function.In summary, different methods were developed to prepare polymeric hollow spheres, composite spheres, microcapsules and core-shell spheres, and extended to the preparation and use of the functional composite microspheres. The synthesis of functional spheres with varied morphologies will provide a novel platform and a change for the applications of polymer spheres in many fields.