Preparation And Electromagnetic Properties Of Core/shell Magnetic Polymers

Magnetic materials with core-shell structure were prepared by comprehensively applying such technologies as liquid phase reaction, surface modification, synthesis in-situ and emulsion polymerization. Four kinds of products were obtained, which were PEG/FeOx ferrofluids, PEG/Fe3O4/ZnOw ferrofluids, PS/FeOx magnetic polymer microspheres and PS/FesOVZnOw magnetic polymers. These four kinds of products were characterized by series advanced analysis technologies of SEM, TEM, XRD, XPS, FT-IR and Element Analysis. The effects on the morphology, phase component and structure of these products were investigated in detail.PEG/FeOx ferrofluids with the collidal particles of nano-scale were prepared through controlling the size and shape of polyethylene glycol (PEG) micelles formed in the hydrosol. The results of XRD and elment analysis showed that the components of the products were mainly influenced by the molar ratio of H2O2 to Fe2+. The TEM images and the size analysis results indicated that the morphology of the ferrofluids was obviously affected by PEG content. The research of FT-IR demonstrated that the organic and inorganic phases were combined by physical adsorption and coordination bond.PEG/Fe3O4 colloidal particles were controlled to form on the surface of zinc oxide whisker by surface modification and synthesis in-situ, thus PEG/Fe3O4/ZnOw ferrofluids were prepared. Microscopic analysis showed that the products were formed through the adhesion of PEG/Fe3O4 colloidal particles on the surface of ZnO whisker.According to the results of FT-IR and XRD analysis, the product was constituted of PEG, Fe3O4, and ZnO phases, a new phase of ZnFe2O4 was also found.With the original materials of PEG/FeOx ferrofluids, PS/FeOx magnetic polymer microspheres with diameters of 30 nm to 16 um were synthesized by emulsion polymerization. The investigation indicated that the product was mainly composed of polystyrene (PS), FeOx, and PEG phases. Moreover, the research demonstrated that the morphology and components of the obtained microspheres were influenced by the kind of core materials, the stirring rate of reaction system, and the content of monomer, emulsifier, initiating agent and medium polarity conditioner.PS/Fe3O4/ZnOw magnetic polymers with cores mainly composed by ZnO and Fe3O4 were primarily synthesized. The morphology observations showed that the products were with some shape of tetra-needle covered by polymer shells. According to the results of FT-IR, XRD and elements analysis, the products were mainly constituted of Fe3O4, ZnFe2O4, PS and PEG phases. Furthermore, the formation process of ZnFe2O4 was suggested.The magnetic properties of the four kinds of products were investigated by vibrating sample magnetometer and the results indicated that all products were hard magnetic materials. Furthermore, the electromagnetic properties of PS/FeOx composite microspheres and PS/Fe3O4/ZnOw composites were studied emphatically, and some valuable conclusions were obtained. As far as PS/FeOx microspheres were concerned, the products appeared dielectric property, however thedielectric loss power was low. On the other hand, the magnetic loss property of the products was good when the frequency was below 4 GHz. The results also showed that the products with higher ferrous content appeared better magnetic loss property. For PS/Fe3O4/ZnOw composites, the magnetic loss property in low frequency band (f<3GHz) was better than that in high frequency band (f>GHz), and the dielectric loss was not observed in the band of 2~ 18 GHz.