Spherical polyelectrolyte brushes: Ideal templates for preparing pH-sensitive core–shell and hollow silica nanoparticles

Monodisperse silica-coated polystyrene core–shell nanoparticles (CSNs) and hollow silica nanospheres with a well-defined morphology and pH sensitivity were prepared using spherical polyelectrolyte brushes (SPBs) as templates. The anionic poly(acrylic acid) SPBs attached on PS cores played a pivotal role in directing and controlling the coating of silica by the Stöber method. A smooth silica shell with a uniform thickness was obtained as observed by SEM, TEM and AFM. Mechanism of silica coating in SPB was discussed. Effects of polyelectrolyte chains, salt concentration and temperature on the structure of silica layer were detailed. The prepared core–shell and hollow silica nanoparticles showed significant pH response and redispersibility as observed by DLS, which should be ideal candidates for promising applications in drug delivery, catalysis and functional materials.