From the Center to the Edge: Deformation-Induced Migration of Silica Nanoparticles within Silica–Polymer Nanocomposite Particle

Disc-like colloidal particles with a multihollow structure were fabricated from submicrometer multicore-shell silica-polystyrene (SiO₂-PS) nanocomposite particles. The synthesis involved seeded dispersion polymerization of 2-ethylhexyl methacrylate (EHMA) using near-spherical SiO₂-PS particles as seeds in the presence of decane, followed by the removal of poly(2-ethylhexyl methacrylate) (PHEMA) and decane. Beyond achieving the disc-like shape, we uncovered a noteworthy phenomenon: the encapsulated silica nanoparticles underwent a remarkable centrifugal migration from the interior to the periphery of the polymer matrix during the deformation process. This deformation-induced migration is attributed to the flow of the polymer phase as the seed particle is compressed into a disc-like shape within the confined "hamburger-like" intermediate structure. A systematic investigation of key polymerization parameters, including the methanol/water mass ratio, the stirring rate, the polymerization time, and the silica nanoparticle size, revealed that this migration process coupled with disc formation occurs over a wide processing window. This work not only provides a robust route to anisotropic composite colloids, but also offers fundamental insights into the control of nanoparticle distribution within deformable polymer matrices.