Composite magnetic microcapsules based on multilayer assembly of ethanol-soluble polyimide brushes and magnetite nanoparticles: preparation and response to magnetic field gradient

Microcapsules consisting of a calcium carbonate core template surrounded by shells containing magnetite nanoparticles and ethanol-soluble polyimide brushes with polymethacrylic acid side chains were assembled using a layer-by-layer technique under nonaqueous conditions. These microcapsules represent a potential solution to the challenging problem of encapsulating water-soluble compounds, particularly low molecular weight drugs. It was possible to move these microcapsules with magnetite nanoparticles in their shells by applying a magnetic field gradient. The novel microcapsules were characterized by optical microscopy, atomic force microscopy, and scanning electron microscopy. Using the brush-like polyanions instead of linear polyanions made it possible to increase the shell thickness gain per ionic assembly cycle by a factor of ~3.