Narrowly dispersed micrometer‐sized composite spheres based on diazonium–polystyrene

Diazonium group–substituted polystyrene (PS–N ) micrometer‐sized spheres with narrow distribution were prepared from highly crosslinked polystyrene particles. Then a composite sphere was prepared with the micro‐PS–N sphere as core and submicrometer‐sized poly(styrene‐methyl methacrylate‐acrylic acid) [P(S‐MMA‐AA)] colloids or nanometer‐sized SiO2 particles as shell via columbic interaction. The ionic linkages between the core and shell convert to covalent bonds in the thermal treatment process. As a result, the composite sphere becomes very stable toward polar solvents as well as toward ultrasonic treatment. A hollow SiO2 micrometer‐sized sphere then was achieved by removing the core under sintering conditions (700 °C).