Toward theta-shaped polymer composite particles by seeded emulsion polymerization

Abstract

Theta-shaped (θ-shaped) polystyrene–poly(glycidyl methacrylate) (PS–PGMA) composite particles have been synthesized by seeded emulsion polymerization using PS seed particles pre-swollen with dibutyl phthalate (DBP) and glycidyl methacrylate (GMA). The effects of key polymerization parameters, including the total GMA/PS mass ratio, the mass ratio of GMA added during the swelling and polymerization stages (G_s/G_p), the amount of DBP, the initiator composition, and the K-value (a viscosity-based molecular weight index) of polyvinylpyrrolidone (PVP) used in seed preparation, are systematically investigated. It is found that a G_s/G_p ratio of around 3.0 : 3.0, combined with an appropriate DBP content, is critical for achieving well-defined theta-shaped solid particles. In contrast, the introduction of a water soluble initiator or PVP with higher K-values leads to multihollow particles with near-spherical or ill-defined theta-shaped morphologies. Furthermore, selective dissolution of the PS composition in the theta-shaped PS–PGMA composite particles can lead to the formation of bowl-like PGMA particles. This work offers a new paradigm for the synthesis of anisotropic functional colloids.