Microgel-silica hybrid particles: Strategies for tunable nanostructure, composition, surface property and porphyrin functionalization

Cationic poly(acrylamide-co-2-(dimethylamino) ethyl methacrylate, methyl chloride quaternized) (poly(AM-co-DMC)) microgels with various cross-linking degrees and compositions were synthesized and used as colloidal templates for controlled formation of microgel-silica hybrid particles at ambient conditions. The combined studies from transmission electron microscopy, solid-state ²⁹Si magic angle spinning NMR spectroscopy, thermogravimetry and aqueous electrophoresis indicated that the porous nanostructure, composition and surface zeta potentials of microgel-silica hybrid particles could be well controlled by simply adjusting the silicification reaction times, cross-linking degrees and compositions of microgels and media composition for silica deposition. Comparative studies from thermogravimetry and X-ray photoelectron spectroscopy on the compositions of microgel-silica particles prepared from different silica deposition times indicated that organic-inorganic composition distribution of hybrid particles is not uniform for whole particles, with silica-rich core and copolymer-rich shell. Furthermore, we demonstrated the facile incorporation of tetra(4-sulfonatophenyl)porphine (TSPP) molecules into microgel-silica particles, leading to the biomimetic formation of porous hybrid particles with bright fluorescent emission features. We expect that these well controlled and functionalized hybrid particles have potential applications for encapsulation, controlled release, labeling or imaging.