Preparation and characterization of multiresponsive polymer composite microspheres with core-shell structure

Fe3O4/SiO2/poly (N-isopropylacrylamide-co-N,N-dimethylaminoethyl methacrylate) [P(NIPAM-co-DMA)] multiresponsive composite microspheres with core-shell structure were synthesized by template precipitation polymerization. First, the magnetite nanoparticles were coated with silica and then modified with 3-(trimethoxysilyl)-propyl methacrylate (MPS). Subsequently, the Fe3O4/SiO2 particles grafted with MPS were used to seed the precipitation copolymerization of NIPAM and DMA. The composite microspheres with core-shell structure were superparamagnetic, pH-sensitive, and thermoresponsive. The swelling ratio (D-25 degrees C,D- (pH = 3)/D-50 degrees C,D- (pH = 9))(3) coupling of pH and temperature increased up to 21.2, which was much higher than that without comonomer DMA.