Mechanism Of The Synthesis Of Hollow Microspheres In Situ Interface

In-situ polymerization is one effective method to prepare hollow structure or hollow spheres. In this thesis, polymer hollow spheres were prepared via in-situ interfacial polymerization in emulsion system. Our research mainly includes five parts. Firstly, polystyrene hollow spheres were obtained by using the vesicle as templates, which were formed by the mixed anionic and nonionic surfactant. Secondly, four types of anionic surfactant (alkyl polyoxyethylene ether sulfonate or carbonate) were synthesized and employed to prepare hollow structure polymer spheres. Thirdly, silica hollow particles were fabricated via an interfacial polymerization in W/O inverse emulsion. Fourthly, ?-ray radiation induced interfacial redox reactions were discussed in detail and polystyrene hollow structure spheres were prepared successfully. Lastly, microcapsules were prepared successfully by adopting polymeizable surfactant in the in-situ interfacial polymerization in W/O inverse emulsion and the process of drug release was characterized.1. The mechanism and the controlling factors were studied to prepare polystyrene hollow spheres using mixed anionic-nonionic surfactants system. By virtue of the phase transformation of nonionic surfactant at its cloud point, hollow spheres of polystyrene were prepared from vesicle templates formed by potassium oleate (KO) and alkyl-phenol polyoxyethylene (n) ether (n=10, OP-10) at 70-80℃. The hollow structure was characterized by TEM and FESEM. The diameter of the hollow spheres varied from 200 nm to 800 nm and the shell thickness was uniformly c.a. 30-50 run.2. Polymer multi-hollow spheres were prepared by using alkyl polyoxyethylene ether sulfocuccinate or carbonate as surfactant initiated by ?-ray radiation. A series of alkyl polyoxyethylene anionic surfactant were synthesized and characterized by FT-IR and NMR. Then the distribution of surfactant in the aqueous and oil phase was measured by weighing method. In experiments, the incorporation of surfactants inside polystyrene particles was clearly observed. Based on this idea, multi-hollow polymer spheres were prepared and this result strongly supports the proposal incorporation mechnism.3. Silica hollow particles have been prepared in W/O emulsion system at room temperature using base (amine or NaOH) as catalyst and TEOS as the silica source. The pH value of aqueous phase, the viscosity of external oil phase and the cationic surfactant were found to be the key factors to the formation of the stable and regular spherical silica hollow particles. When the pH value of aqueous phase was controlled between 8 and 9, silica hollow particles could be fabricated. The kinetics of the formation of silica hollow particles was believed to be based on the difference between the hydrolysis rate and the condensation rate of TEOS, which can be skillfully adjusted by the pH value. At the same time, the effect of the type of amine, amount of surfactant, and the ratio of water to oil has been discussed in detail.4. The motivation of this work is to explore the formation mechanism of polymer microcapsules via ?-ray radiation in W/O inverse emulsion system. Utilizing the strong reducing radical (hydrated electron) and oxidant radical (hydroxyl radical) produced in the aqueous phase by ⁶⁰Co ?-ray radiation, two interfacial redox initiation systems were proposed and applied to the preparation of polymer microcapsules. In this work, benzoyl peroxide (BPO)-hydrated electron and N, N-dimethyl aniline (DMA)-hydroxyl radical were used to control the polymerization position at the water-oil interface, respectively. Finally, polystyrene (PS) microcapsules were synthesized successfully. From the kinetic curves of monomer conversion, the mechanism of radiation induced interfacial reaction was determined and this method can be extended to synthesize polymer capsules and composite spheres.5. Polymerizable surfactant (12-acryloxy-9-octadecenoic acid, AOA) was introduced into the W/O inverse emulsion to control the in-situ interfacial polymerization induced by ⁶⁰Co ?-ray and polystyrene microcapsules were successfully synthesized. Free-radical polymerization was constrained to the interface of water-in-oil emulsion by the copolymerization of AOA and styrene. The shell thickness can be controlled by the content of monomer. The hydrophobic hollow microspheres were used to encapsulate a large amount of sodium salicylate directly and released the compound into water at a tunable rate depending on the amount of monomer added to the oil phase during the polymerization. This study demonstrates the potential of hollow microspheres, prepared from ⁶⁰Co ?-ray induced in-situ interfacial polymerization, as drug carriers in controlled drug release applications.