Study On Preparation Of Functional Polymeric Microspheres

With the development of preparation technologies, polymeric microspheres with specific function, such as core-shell structured polymeric microspheres, magnetic polymeric microspheres, environment responsive microspheres, and hydrophilic polymeric microspheres, have been widely and deeply researched. In recent years, due to the requirements of biomedicine and bioengineering fields including drug carrier, targeted-drug delivery system, and cell separation, magnetic polymeric microspheres and polymeric microspheres with reactive groups (COOH, CONH2, NH2)on surface have been widespread concerned in the scientific community. In this paper, the preparation of PMMA-Fe3O4 composite nanospheres and hydrophilic microspheres with groups of COOH and CONH2 on surface were studied. The main content of the paper are as following:1 Fe3O4 magnetic nanoparticles were prepared via chemical co-precipitation method. The obtained Fe3O4 magnetic nanoparticles were characterized by means of FTIR, X-ray diffraction (XRD) and VSM. The results reveal that the Fe3O4 magnetic nanoparticles with an average diameter of 15 nm, cubic shaped and superparamagnetic. Then, the surfaces of Fe3O4 magnetic nanoparticles were modified with different surfactants to achieve stable water-based magnetic fluid. The stabilizing capability of different surfactants, as well as the effects of surfactant concentration on the size and shape of water-based magnetic fluid particles were investigated.2 With the water-dispersible Fe3O4 nanoparticles modified with oleic acid and sodium oleate (water-based magnetic liquid) as seed emulsion, KPS or AIBN was used to initiate the copolymerization of MMA and sodium oleate on the surface of Fe3O4 nanoparticles. The results of TEM, DTS and FTIR characterization shew that PMMA successfully wrapped around the Fe3O4 nanoparticles. The effects of initiator type and concentration of water-based magnetic fluid on the polymerization system were investigated. Result indicated that it is more prone to form blank PMMA particles without magnet when using KPS as the initiator. Increasing the concentration of water-based magnetic fluid, the rate of conversion of MMA enhanced, but the shape of the obtained PMMA-Fe3O4 magnetic polymeric microspheres became poor, and strips or netted irregular structures were prone to be formed.3 Hydrophilic polymeric microspheres with COOH and CONH2 were prepared from acrylonitrile (AN) by two steps. In the first step, crosslinked polyacrylonitrile (PAN) nanospheres were prepared by copolymerization of AN monomer and MBA cross-linking agent. In the second step, the PAN nanospheres were alkaline hydrolyzed to form hydrophilic polymeric microspheres with COOH and CONH2. The crosslinked PAN nanospheres and hydrophilic microspheres were characterized by means of DTS, FTIR, element analysis, TEM. The influence of the hydrolysis time on the properties of the resulting hydrophilic microspheres was investigated. The result indicated that the CN groups were turned to COOH or CONH2 after hydrolysis. The longer of hydrolysis, the more amount of COOH or CONH2 groups there were on the surface of spheres, the bigger the spheres would be. Within 6 hours of hydrolysis, the obtained products were mainly composed of polyacrylamide and a amount of polyacrylic acid.