Preparation Of Organic-Inorganic Nanocomposite With Special Structures From Pickering Emulsion Polymerization And Study Of Their Applications

With the development of interface science and technology, We can obtain nano-composite particles with various structures (core-shell, capsule, etc) by "design of structure" and get different specific application performances. In this way, the advantages of polymer materials and inorganic materials can be linked. At present, according to features and functions of practical application to design materials and prepare applicable materials are the common goal of scientific community and industrial circles. In this thesis, polystyrene/nano-SiO2 composite microspheres (PS/nano-SiO2) with core-shell structure, magnetic polymer enhanced hybrid capsules, poly(acrylamide)/silica hybrid microspheres and poly(N-isopropyl-acrylamide)/poly(methyl methacrylate)/silica hybrid capsules were prepared from Pickering emulsion polymerization. The preparations, characterizations and applications of these materials were studied. The main research works are summarized as follows:1. Nano-silica particles were modified by y-methacryltrimethoxysilane. The effects of solvent type, pH value of water in solvent, water content in solvent, mass of modifier and temperature for modification on modification (contact angle) were investgated. The results indicated:cyclohexane/water solvent, slightly acidic aqueous phase in solvent, lower water content and reaction temperature of 50-70℃are better for modification. The prepared modified silica particles aggregate in water but well dispersed in ethanol. 2. Pickering emulsion (styrene/water) stabilized by silica nanoparticles were investgated here. The following conclusions are drawn:Particle wettability and the priority wettability have significant effect on the particles location in Pickering emulsion system, and the type of prepared emulsion. Solid particles with too hydrophilic (contact angle is 9.2°) or hydrophobic (128.5°) can not be used as a stabilizer for emulsion preparation. The particles with moderate hydrophilicity (41.5°) can stabilize O/W emulsions;For the particles (with a contact angle of 87.2°), the prior wettibility decide the type of emulsion-the O/W emulsion is formed when particles are dispersed in water preferentially, W/O emulsion is formed when particles are dispersed in styrene preferentially. For O/W emulsion stabilized by the particles with a contact angel of 41.5°, the lower particle surface charge or higher particle concentration or lower emulsion temperature are better for the stability of as-prepared emulsion. The droplet size in Pickering emulsion decrease as increasing the particle concentration.3. Polystyrene/nano-SiO2 composite microspheres (PS/nano-SiO2) with core-shell structure were successfully synthesized in a Pickering emulsion route using nano-SiO2 particles as stabilizers, which were organically modified by methacryloxypropyl-trimethoxysilane (MPTMS) which containing a reactive C=C bond. The products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transformation infrared spectrum (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). In addition, bare PS spheres could also be obtained by changing synthetic conditions. It was found that the morphology of the resulting products depends on particle concentration, particle wettability and pH value of particle dispersion. A possible mechanism for the formation of the composites with different morphologies is proposed.4. Magnetic polymer enhanced hybrid capsules (MPEHCs) were successfully prepared from a novel Pickering emulsion polymerization. The resultant products were characterized by Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Fourier transform infrared spectrum (FTIR), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Vibration sample magnetometer (VSM). It was proved that the MPEHCs consist of SiO2 outer shell and magnetic polymer inner shell with particle sizes from 0.8μm to 2μm and thickness about 140 nm. The MPEHCs were applied as a drug carrier to study their controlled release behaviors and ibuprofen was used as a model drug. The curve of release behaviors of ibuprofen exhibited a typical sustained release pattern, indicating that the MPEHCs could be applied as a promising drug vehicle for controlled release systems.5. Poly(acrylamide)/silica hybrid microspheres were prepared from inverse pickering emulsion polymerization using a acrylamid aqueous solution as the inner droplets, liquid paraffin as the outer continuous phase and modified silica nanoparticles as stabilizers. These hybrid capsules sized about 2-4μm, and they contained a solid silica shell and a Poly(acrylamide) core. In the process of the preparation, both the concentrations of AM and solid particles can bring a notable influence on the synthesis of the capsules. The prepared Poly(acrylamide)/silica hybrid microspheres had a strong adsorption of Hg2+ in the wastewater and the effect of the adsorption, which is not much influenced by temperature, can be better in the weak acid condition. At 30℃, the adsorption isotherms fit the Langmuir isotherms equation very well. Meanwhile, the adsorption of Hg2+ by the hybrid microspheres agrees with Pseudo-first-order adsorption kinetic process.6. Poly(N-isopropylacrylamide)/poly(methyl methacrylate)/silica hybrid capsules were prepared from inverse Pickering emulsion polymerization. A N-isopropylacrylamide aqueous solution was emulsified into an oil phase containing methyl methacrylate and divinyl benzene by sonication to obtain a W/O Pickering emulsion using modified silica nanoparticles as stabilizers. After the emulsion was polymerized, the hybrid capsules were obtained. The capsule wall contained two layers-a solid particle monolayer and a polymer layer and the wall thickness could be controlled by adjusting the methyl methacrylate and divinyl benzene concentrations in the continuous oil phase before polymerization. The as-synthesized capsules exhibited temperature-responsive properties. The controlled release experiments showed that the release rate of a model drug from the hybrid capsules could be controlled by adjusting the wall thickness of the capsule or the temperature of the release medium. 7. Rotating packed bed was used to prepare inverse Pickering emulsion. The stability of the Pickering emulsions has a relationship with the solid particle concentration, rotating speed and circulaton time. Higher particle concentration or rotating speed and longer circulation time can improve the stability of Pickering emulsions. Emulsion droplet size becomes smaller as increment of particle concentration or rotating speed, or extension of circulation speed.