Synthesis of Multihollow Polystyrene-Silica Nanocomposite Particles by Solvent Swelling

Multihollow polymer-silica nanocomposite particles combine the advantages of multihollow architectures with those of organic-inorganic nanocomposite particles, yet their synthesis remains challenging and rarely reported. In this work, a convenient route has been developed to synthesize multihollow nanocomposite particles from submicrometer-sized polystyrene-silica (PS-SiO₂) nanocomposite particles via swelling in a THF/water mixture and subsequent drying. The influence of key swelling parameters, including the THF concentration, the stirring rate, the swelling time, and the surfactant concentration on the formation of the multihollow nanocomposite particles, is investigated. Optimal conditions (70 vol % THF, 300-500 rpm, 6 h swelling, 10 mg mL^-1 SDS) afforded nearly 100% multihollow particles with a mean diameter of ∼1.43 μm, significantly larger than the original particles (∼341 nm), while the silica shell remained intact on the surface. The formation mechanism is proposed to involve THF-induced swelling and plasticization of the PS core, phase separation of water/THF domains within the swollen polymer, and fixation of the hollow structure upon solvent removal. This approach represents a new paradigm in the synthesis of multihollow polymer colloids without requiring specially functionalized polymer precursors.