Preparation of nanocapsules via emulsifier-free miniemulsion polymerization.

Nanocapsules containing hexadecane or paraffin as core materials and polystyrene as a shell were produced in a new method through emulsifier-free miniemulsion polymerization using 2,2' azobis (2-amidinopropane) dihydrochloride (V-50) as a cationic ionizable water-soluble initiator. The effect of some parameters such as hexadecane or paraffin amounts and polymerization duration on morphology and thermal properties of resulting nanocapsule particles was studied. Transmission electron microscopy (TEM) showed that the products had latex particles having a size range of about 200-700 nanometer and both nanocapsules with core-shell morphology and solid particles. The phase change temperature and phase transition heat of the produced nanocapsules were determined by differential scanning calorimetric (DSC) analyses. Thermogravimetric analysis (TGA) was also used to prove the capsulation and to determine the amount of hexadecane or paraffin in the nanocapsules.