Preparation Of Inorganic/polymer Nanocomposite Microspheres Via Miniemulsion Polymerization

As a novel method, miniemulsion polymerization has gained sufficient ratification and extensive spread in late decades. It has applied in industry abroad. Its advantages appear gradually, with the mechanism of miniemulsion being explored. Compared with common emulsion polymerization, miniemulsion has a smaller size of50-500nm, which is a great breakthrough in the area of smaller size. Moreover, as the more strict requirements of environmental protection and enhanced environment protecting consciousness, the amount of surfactant used in emulsion polymerization has been an important factor. A mass of surfactant used in emulsion polymerization affects the property of the final products, and pollutes the environment. But miniemulsion uses the least amount of surfactant, and guarantees the stability of latex. Especially, the polymerizable macromolecule surfactant used in miniemulsion makes it being green polymerization.In the first chapter, the research process of preparation of inorganic/polymer composite microsphere via miniemulsion is introduced, with miniemulsion polymerization as the main clues. Applied process of waterborne polyurethane as surfactants in miniemulsion polymerization, together with miniemulsion preparation of biomimetic materials are also introduced.In the second chapter, the preparation of SiO2/PMMA composite microspheres via miniemulsion polymerization was introduced. The carboxylic waterborne polyurethane was synthesized with isophorone diisocyanate(IPDI), polyether glycol(N210) and2,2-bis(hydroxymethyl)propionic acid(DMPA) as the major materials, and terminated by C=C from β-hydroxyethyl methacrylate(HEMA). SiO2/PMMA composite microspheres were prepared with different type of initiators by double in situ miniemulsion polymerization, in which the waterborne polyurethane was used as a polymerizable surfactant. The prepared products were characterized by TEM, FTIR and TGA, respectively. The results indicate that morphologies of the SiO2/PMMA composite microsphere prepared by waterborne polyurethane surfactant are different from those prepared by conventional micromolecule surfactants. The type of initiators affects significantly on the morphologies of the SiO2/PMMA.In the third chapter, the method of in situ biomimetic synthesis of nHA/PMMA composite microspheres was introduced. nHA/polymer composite microspheres with the size of250nm were in situ biomimetic synthesized in the aqueous phase at37℃for7days by using the surface-functionalized polymeric nanoparticles as templates. A miniemulsion process was adopted to prepare the cross-linked templates via the co-polymerization of methyl methacrylate (MMA) and methyl acrylic acid (MAA). The functional groups (-COOH) were bound on the surface of polymeric nanoparticles. By utilizing the-COOH groups absorbing Ca+followed by HPO42-in certain pH conditions, hydroxyapatite (HA) crystal nucleus formed and grew up to be rod-like crystals on the surface in this system. Thus, nHA/polymer composite microspheres are successfully obtained, and studied by Fourier transform-infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), and transmission electron microscopy (TEM). The morphology of the polymeric nanoparticles and composite microspheres was investigated by (TEM). In the TEM images of polymeric templates, plenty of nanoparticles about200nm were observed. And some unsmooth nanoparticles with the larger size of250nm were presented in the TEM images of composite microspheres. The inorganic component, increased in size of the50nm in composite microspheres, confirmed to be low crystallized HA in nanoscale by XRD, which is similar to that of skeleton. Together with FT-IR, they showed that nHA was fabricated on the surface of polymer microspheres. Also, its adsorption studies on salicylic acid (SA) are investigated. The composite microspheres were dispersed in SA solution under constant stirring. After the SA adsorbed by the composite microspheres in certain time, the content of residual SA was detected using UV. It’s also revealed that SA can be absorbed by composite microspheres. The intensity of absorption increases with the increase of the initial concentration of SA, and the absorption reaches equilibrium after5h at a fast speed. These nHA/polymer composite microspheres have great potential in bone tissue regeneration, drug delivery and bone materials loaded with drugs.In the fourth chapter, the preparation of narrowly size-distributed hybrid hollow microspheres via double in-situ inverse miniemulsion polymerization and interfacial sol-gel process was introduced. Hybrid hollow microspheres with a narrow size distribution were successfully prepared via in-situ interfacial hydrolysis and condensation reactions of tetraethoxysilane (TEOS) based on the templates of cross-linked polymer nanocapsules, which were synthesized via in-situ inverse miniemulsion copolymerization of acrylamide (AM) and divinylbenzene (DVB). The inverse miniemulsions containing pH-controlled hydrophilic droplets were first prepared via homogenizer by using Span-80and cetyltrimethylarnmonium bromide (CTAB) as surfactants. TEOS was directly introduced to the continuous phase of an inverse miniemulsion. The silica shell was formed via interfacial sol-gel process by the deposition of silica on the surface of polymer nanocapsules. The formation of hybrid hollow microspheres morphology was confirmed by transmission electron microscopy (TEM), and the size and size distribution were measured by dynamic light scattering (DLS). The thermal performance and SiO2content were verified by thermogravimetric analysis (TGA). The results show that the prepared hybrid hollow microspheres have narrow size distributions in range of230-350nm. And they have a real empty core and a two-layer shell structure, with a thickness of30nm of the polymer layer and20nm of the silica layer.