Preparation of aqueous dispersible styrene-maleic amide encapsulated CoAl ₂O ₄ nanocrystals using supercritical water flow type apparatus

Styrene-maleic amide (SMA) encapsulated cobalt blue nanocrystals were synthesised by the supercritical water method using a flow type reactor. A monodisperse, water dispersible nanocrystal blue pigment with the particle size of 5 nm was obtained by SMA encapsulation. Influence of different reaction conditions such as polymer concentration, pH, encapsulation temperature, etc., on the encapsulation and optical property of the cobalt blue nanocrystals is studied in detail. About 6-8 wt-% SMA concentration and the encapsulation temperature between 270 and 300°C were found to be favourable conditions for successful SMA encapsulation. This novel polymer encapsulation process could be used for mass production of different polymer inorganic hybrid materials that can be used in a variety of applications such as metallic finishing, contrast enhancing luminescent pigments, paint production, electronics and high end optical filters.