The Preparation And Application Of Carboxyl-Functional Monodisperse Polystyrene In Emulsion Polymerization

In this thesis, emulsifier-free emulsion polymerization method was employed to prepare carboxyl-functional monodisperse cross-linked polystyrene microspheres, whose applications in preparation of anisotropic microsphere via seeded emulsion polymerization phase separation method and in Pickering emulsion were studied. The main results are summarized as follows:1. Preparation of polystyrene microspheres via emulsifier-free emulsion polymerization: potassium persulfate was used to induce copolymerization of acrylic acid and styrene, resulting in the formation of submicron-sized carboxyl-functional monodisperse cross-linked polystyrene microspheres.2. Preparation of anisotropic microsphere via irradiated seeded emulsion polymerization phase separation method: the submicron-sized anisotropic microspheres with different morphologies were obtained by irradiated seeded emulsion polymerization, in which styrene was used as the second-stage monomer and carboxyl-functional monodisperse cross-linked polystyrene microsphere as the seed microspheres. It was found that when the ratio of the polystyrene seeded microspheres with 5‰cross-linker to the second-stage monomer was 0.2:1 with absorbed dose rate of 11 Gy/min and pH=7, snowman-like microspheres were formed at high yield. The influences of the ratio of seeded particles to monomer, the pH value, absorbed dose rate, the concentration of divinyl benzene for the second-stage monomer and the amount of cross-linker of the seed particles on the morphology of the anisotropic microsphere were also discussed.3. Preparation of multi-hollow microsphere via Pickering emulsion polymerization: The multi-hollow polystyrene microspheres were obtained successfully via Pickering emulsion polymerization byγ-radiation at certain conditions, in which the carboxyl-functional monodisperse cross-linked polystyrene microsphere adjusted to a certain pH value and the nonionic emulsifier Tween-60 were used as surfactants. By the way, the effects of the absorbed dose rate, the amounts of polystyrene solid emulsifier and Tween-60 on the morphology of the multi-hollow microspheres were also studied.