Controlled radical polymerization based on 1, 1-diphenylethylene (DPE method) was used to prepare pH-responsive magnetic composite microspheres. By this method, Fe₃O₄/Poly (acrylic acid-stat-methyl methacrylate-block-(2-dimethylamino) ethyl methacrylate) (Fe₃O₄/P(AA-MMA-DMA)) microspheres were prepared via emulsifier free emulsion polymerization of acrylic acid (AA), methyl methacrylate (MMA) and (2-dimethylamino) ethyl methacrylate (DMA) using 1, 1-diphenylethylene (DPE) as radical control agent in the presence of Fe₃O₄ nanoparticles. The structure and properties of Fe₃O₄/P (AA-MMA-DMA) microspheres were characterized by IR, ¹H NMR, SEC-MALLS, TEM, TGA, VSM and DLS. The application of Fe₃O₄/P (AA-MMA-DMA) microspheres in controlled release of drug was also investigated. It was found that the DPE method allowed the preparation of pH-responsive magnetic composite microspheres, and Fe₃O₄/P (AA-MMA-DMA) microspheres obtained were pH-responsive, perfect sphere-shaped morphologies, superparamagnetism with a saturation magnetization of 14.36 emu/g, and high magnetic content with a value of 29%. Moreover, Fe₃O₄/P (AA-MMA-DMA) microspheres could control the release of phenolphthalein in a buffer solution by adjusting the pH value.

http://www.sciencedirect.com/science/article/pii/S0928493111000567