Magnetic polystyrene nanocapsules with core-shell morphology obtained by emulsifier-free miniemulsion polymerization

Nanocapsules containing hexadecane and Fe 3 O 4 magnetic nanoparticles as core materials and polystyrene as shell were produced in a new method through emulsifier-free miniemulsion polymerization using 2,2′-azobis(2-amidinopropane) dihydrochloride (V-50) as a water-soluble initiator. The effect of some parameters such as the amounts of Fe 3 O 4 and initiator on morphology of resulting nanocapsules was studied. Transmission electron microscopy showed that the products had latex particles having a size range of about 300–1300 nanometer and both magnetic nanocapsules with core-shell morphology and solid particles. The phase transition temperature and phase transition heat of the produced capsules were determined by differential scanning calorimetric analyses. Thermal properties of the latex were compared with those of magneticparticles-free latex and with those of latex free of both magnetic particles and hexadecane. Thermogravimetric analysis was also used to confirm the encapsulation and to determine the amounts of hexadecane and Fe 3 O 4 within the capsules.