Facile Preparation Of Monodisperse Functional Polymer Microspheres And Their Magnetic Composite Microspheres

In recent years, more and more attentions have been attracted on the synthesize of the monodisperse functional polymer microspheres and the organic/inorganic composite microspheres. These composite microspheres have many applications, such as in drug delivery, biomacromolecules purification, biosensor and enzyme immobilization. Among the organic/inorganic composite microspheres, magnetic hybrid microspheres have attracted more attention, the reason is that these magnetic hybrid microspheres not only exhibiting magnetic susceptibility to an external magnetic field, but also easily further functionalized and surface-modified by the attachment of various bioactive molecules, they can conveniently separate the objective biomolecules from the medium with the help of magnets. These merits are very important to some biomolecules thanks to less injury.Based on the research background, this thesis is focused on the preparation of functional polymer microspheres and their magnetic-silica composite microspheres. At first, the monodisperse poly(St/DVB/GMA) microspheres were prepared by soap-free emulsion polymerization and further functionalized using thiol-epoxy "click-chemistry" of surface pendant epoxy groups with functional thiols. Then two kinds of magnetic-silica composite microspheres were prepared based on the above polymer microspheres. Finally, the DNA separation properties of the magnetic composite microspheres have been studied. The detailed results are listed as follows:(1) Monodisperse poly(St/DVB/GMA) microspheres (PMs) were prepared by soap-free emulsion polymerization and the surfaces of the PMs were further functionalized by the thiol-epoxy "click-chemistry" of surface pendant epoxy groups with functional thiols. A variety of functional groups were successfully grafted to the PNs surfaces at high densities as exemplified by the reactions with 2-aminoethanethiol, thioglycolic acid, and 2-mercaptoethanol. The adsorptions of acid orange and toluidine blue to, respectively, the 2-aminoethanethiol and thioglycolic acid functionalized PMs were examined, which fitted well to the Langmuir isotherm model. Experimental results showed that the functional polymer microspheres possessed excellent adsorption properties for the organic dye. The surface amino group density was found to be 1.1 mequiv/g, with an adsorption capacity of 398 mg/g of acid orange; while the thioglycolic acid modified PMs displayed 1.4 mequiv/g carboxylate groups and an adsorption capacity of 416 mg/g for toluidine blue.(2) Two kinds of magnetic-silica composite microspheres (MP1@SiO2 and MP2@SiO2) were prepared with two different methods. MP1@SiO2 composite microspheres were prepared by direct deposition of Fe3O4 onto the surface of PSGD-COOH, and then the composite microspheres were coated with SiO2 by sol-gel process. MP2@SiO2 composite microspheres were prepared by the direct interaction of PSGD-NH2 and sodium citrate modified Fe3O4 nanoparticles, then coated with SiO2. According to the data of MP1SiO2 and MP2@SiO2 in DNA adsorption capability, we can find that the adsorption amount of DNA is similar, both are around 16 mg/g. The second preparation process is optimum, it is facile and well controlled, and the adsorption efficiency of DNA is excellent.