Synthesis of liquid-filled nanocapsules via the miniemulsion technique

This study describes the synthesis of well-defined nanocapsules via the miniemulsion technique. Pentaerythritol tetrakis(3-mercaptopropionate) (TetraThiol) or 1,6-hexanediol di(endo, exo-norborn-2-ene-5-carboxylate) (DiNorbornene) is used as the oil phase. TetraThiol is encapsulated via the miniemulsion technique without polymerization, as this monomer would simultaneously act as a chain-transfer agent, and DiNorbornene is encapsulated via miniemulsion polymerization of styrene. Various styrene-maleic anhydride (PSMA) copolymers and poly(styrene-maleic anhydride)-block-polystyrene (PSMA-b-PS) block copolymers were used as surfactant for the synthesis of well-defined nanocapsules with TetraThiol as the core material. The nanocapsules had a diameter of 150–350 nm and the particle size distribution was narrow. The use of PSMA-b-PS block copolymers as surfactant in combination with post-addition of formaldehyde provided improved stability to the nanocapsules. DiNorbornene was encapsulated via miniemulsion polymerization of styrene, and a stable latex with a bimodal particle size distribution was obtained. The distribution of small particles had a size of 60 nm and the distribution of large particles had a size of 150 nm.