One-Pot Seeded Emulsion Polymerization for Janus Particles with Various Morphologies Regulated by Monomer Plasticization and Flow Field

Abstract

For Janus particles, it is crucial to effectively control and regulate their segmented morphologies. In this study, flow field and plasticization are introduced as novel factors in seeded emulsion polymerization, which is a widely used method for preparing Janus particles to regulate the morphology of the as-synthesized Janus particles. Rapid swelling with monomer (3-methacryloxypropyltrimethoxysilane, MPS) renders the polystyrene (PS) hollow particle seeds plasticized and deformable, while an appropriate flow field facilitates the flattening of these plasticized spherical seeds into disc-like particles. Meanwhile, the polymerization of MPS induces phase separation between the PS seeds and as-formed silica bulges, leading to the formation of PS@silica Janus particles. Thus, the deformation of the PS seeds and the growth of silica bulges are carried out in one pot. By adjusting the stirring speed and monomer ratio, Janus particles with various morphologies, from snowman-like to mushroom-like, can be achieved in a controlled manner. Consequently, the Janus balance (JB) and thus the amphiphilicity of Janus particles can be easily adjusted through the degree of seed deformation, allowing for their further application as solid surfactants to stabilize Pickering emulsions with different types and microstructures.