Preparation Of Surface Functional Polymer Microspheres Via Pickering Emulsion Polymerization

As one of the important functional materials, functional polymer microspheres have been widely used in biotechnology, pharmaceutics, information technology, econometric analysis, chromatographic separation, and electronic devices. Surface functionalization of polymer microspheres has become a significant tool for preparing functional polymer microspheres, typically divided into two categories: surface morphology modification and functional materials grafting. Surface morphology modification involves the formation of the rough surface or the porous structure to create large surface areas, while functional materials grafted on the surface include polymer chains, inorganic particles, and functional groups.Pickering emulsion polymerization has been regarded as an important method for functional inorganic particles deposited on the surface of polymer microspheres. In addition, functional groups such as carboxyl and sulfonic acid groups can be grafted on the surface to achieve the design for the surface structure of polymer microspheres, due to the specific interaction between the functional monomers and inorganic particles.In this thesis, hydrophilic titania nanoparticles were prepared by the controlled nonhydrolytic sol-gel method, followed by the modification using the self-made surfactant with a double bond. TiO2-PS composite microspheres were prepared via Pickering emulsion polymerization stabilized by modified titania nanoparticles. The results indicate that the surface modification of titania hydrosols by different amount of the surfactant can greatly affected the structure of the inorganic particles flocs, and thus the regulation of the particle size and size distribution on polymer microspheres is implemented. The mechanism of Pickering emulsion polymerization stabilized by modified titania nanoparticles was proposed.Two surfactants were synthesized by the same method. The only difference between the two is that one has a double bond, but the other does not. The mixture of two surfactants was used for the surface modification of titania hydrosols. TiO2-PS composite microspheres were prepared via Pickering emulsion polymerization stabilized by modified-titania nanoparticles. The results suggeste that the variety on the ratio of the two surfactants can bring few influences on the surface properties of titania hydrosols if the total additions (4wt%) of the two surfactants remains constant. As a result, the size of the final polymer composite microspheres is kept to about100nm. Owing to the different chemical structures of two surfactants, the surfactant with a double bond can be grafted onto the surface of the polymer microspheres in order to achieve the fine adjustment of the functional groups on surface. Too many or too few sulfonic acid groups grafted on surface are not conducive to the suspension dispersion of polymer microspheres in non-polar solvents. The results of electrophoresis experiments show that the surface-modified polymer microspheres have the ability of electrophoresis. After theoretical calculations, several thousand of elementary charges on the surface of every polymer microsphere with the size of100nm can meet the requirements of bistable electrophoretic displays.