A Novel Route to Prepare Fe_3O_4/P(MAA-co-NVP) Cross-Linked Magnetic Composite Microspheres with Core-Shell Architecture by Surface-Initiated Radical Dispersion Polymerization

摘要

A novel route was proposed to design and construct a magnetic composite microsphere with a controllable and regular core-shell architecture, which consists of Fe_3O_4 nanoparticles chemical-covalently encapsulated with pH-smart poly(methacrylic acid-co-N-vinyl pyrrolidone) (P(MAA-co-NVP)) cross-linked copolymers by a surface-initiated radical dispersion polymerization approach. The multistep surface treatment was employed to improve the dispersity and surface-chemical reactivity of Fe_3O_4 nanoparticles, involving introduction of active-NH_2 groups, coupling of 1,1-methylene bis-(4-isocyanato-cyclohexane) and immobilizing of 2,2'-azobis[2-methyl-N-(2-hydroxyethyl) propionamide]. The structure and morphological characterization were carried out by FTIR, TEM, SEM and XRD etc. The neat Fe_3O_4 nanoparticles take on an aggregated spherical shape with an average diameter of about 12 nm, while Fe_3O_4/P(MAA-co-NVP) magnetic microspheres assume regularly monodispersed spheres with a mean dimension of ca. 0.8 μm. The dimension of the microspheres is abruptly increased with increasing pH values of the media. The microspheres exhibit superparamagnetic properties. It is expected that this type of novel microspheres can be employed as a magnetic targeted and pH-sensitive drug carrier.