Toward theta-shaped polymer composite particles by seeded emulsion polymerization

Abstract

Theta-shaped (two-lobed) 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 (Gs/Gp), 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 Gs/Gp ratio 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 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 PGMA-PS composite particles can lead to the formation of bowl-like PGMA particles. This work offers a new paradigm for the design of anisotropic functional colloids.