Synthesis of pH-sensitive hollow polymer microspheres with movable magnetic core

The pH-sensitive hollow poly(N,N′-methylenebisacrylamide-co-methacrylic acid) (P(MBAAm-co-MAA)) microspheres with movable magnetic/silica (Fe3O4/SiO2) cores were prepared by the selective removal of poly(methacrylic acid) (PMAA) layer in ethanol/water from the corresponding Fe3O4/SiO2/PMAA/P(MBAAm-co-MAA) tetra-layer microspheres, which were synthesized by the distillation precipitation copolymerization of N,N′-methylenebisacrylamide (MBAAm) and methacrylic acid (MAA) in the presence of Fe3O4/SiO2/PMAA tri-layer microspheres as seeds in acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as the initiator. The Fe3O4/SiO2/PMAA tri-layer microspheres were afforded by the distillation precipitation polymerization of MAA with 3-(methacryloxy)propyl trimethoxysilane (MPS)-modified Fe3O4/SiO2 core-shell particles as the seeds. The functional multi-layer inorganic/polymer microspheres and the corresponding hollow polymer microspheres with movable magnetic cores were characterized with transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectra, dynamic light scattering (DLS), and vibrating sample magnetometer (VSM).