Study On Preparation Of Functionalized Magnetic Polymer Microsphere And Characteristic Analysis Of Thermogravimetry Curve

Since the 1970s, magnetic polymer microspheres have been found unprecedented applications in biomedical fields not only because of their easy surface functionalization and microstructure control during synthesis procedure, but also due to their fast response to the magnetic field which facilitates an automatic manipulation.The wide applications call for quite different characteristics of magnetic microspheres including their size and size distribution, surface functional groups and group density, magnetic responsiveness and microstructure. To meet the increasing demand, recently, more and more researchers transfer their interests to manipulate the surface modification and microstructure of magnetic polymer microsphere for extending their application and achieving better performance in the procedures.Thermogravimetry Analysis is one of the most important and effective means to characterize materials and is used conveniently and commonly in characterization of the magnetic substance content in magnetic polymer microspheres. Therefore, research on characteristics of TG curves of the magnetic polymer microspheres and the accurate calculation of the magnetic substance content are particularly important. In this paper, the modified seed-emulsion polymerization method to prepare sub-micron/micron carboxyl-functionalized magnetic polymer microspheres was used. Furthermore, by system analysis of the magnetic polymer microspheres TG curve, we found unusual mass loss in high temperature region, and then its cause and accurate calculation method of the magnetic substance content were proposed.1) In this paper, we prepared submicron carboxyl-functionalized superparamagnetic microspheres via the modified seed-emulsion polymerization method. Employed as seeds, 0.60μm Fe3O4 magnetic aggregation droplets were mixed up with monomer droplets of styrene and divinylbenzene to obtain the microsphere whose surfaces were functionalized through the copolymerization of acrylic acid. The effects of the amount of magnetic aggregation emulsion, ratio of crosslinking monomer and the addition of functional monomer on magnetic polymer microspheres microstructure (asymmetric or dispersed) were studied. The microstructure manipulation preliminary mechanism was also proposed. Size, microstructure and magnetic properties of functional magnetic polymer microspheres were characterized by dynamic light scattering particle size analyzer (DLS), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and so on .2) To improve magnetic responsiveness,the carboxyl-functionalized magnetic polymer microspheres of micron scale which contain higher content of magnetic nanoparticles were prepared via using a larger size of magnetic aggregation droplet as seed. Magnetic polymer microspheres we prepared have a uniform size distribution and size in the 1.1~1.9μm, the magnetic substance content of 10wt% to 30wt%, surface carboxyl density of 0.13~0.81mmol/g. Microspheres have a strong magnetic responsiveness to the magnetic field ,and their surface carboxyl groups density are easily controlled. Otherwise, We studied the effect of magnetic aggregation emulsion amount on the microstructure and the effect of acrylic acid amount on surface carboxyl density.3) By system analysis on the TGA curves characteristic of magnetic polymer microspheres and the change of component during the measurements, we found unusual mass loss in high temperature region by characteration of Thermogravimetric Analysis and Mass Spectrum (TG-MS),Ramen Spectroscopy(RS),X-ray Photoelectron Spectroscopy(XPS). TGA measurement are made in atmosphere of nitrogen and oxygen, we proposed two calculation methods and compared them with the results of vibrating sample magnetometer (VSM) to put forward accurate method of the magnetic substance content calculation .