Preparation and characterization of nano‐CaCO3 encapsulated by copolymerization of styrene and maleic anhydride

Encapsulated nanometer calcium carbonate (nano‐CaCO₃) was prepared using styrene and maleic anhydride (MAH) copolymer in 2‐propanol or methanol–water mixture in the presence of different initiator systems. The particle morphology and physical properties of the encapsulated nano‐CaCO₃ particles, such as the interaction between the encapsulating polymer and the nano‐CaCO₃, and the thermal stability of encapsulated nano‐CaCO₃ were studied by Fourier‐transform infrared spectroscopy (FTIR), Soxhlet extraction experiments, thermogravimetric analysis banded with FTIR (TGA‐FTIR) and transmission electron microscopy (TEM). The encapsulating ratio and the stable encapsulating ratio of encapsulated nano‐CaCO₃ were characterized. The results showed that a strong interfacial interaction was obtained due to the formation of a chemical bond or ion‐dipole between the C?O group of MAH and Ca²⁺ ion of nano‐CaCO₃. The encapsulating ratio and stable encapsulating ratio of nano‐CaCO₃ initiated by AIBN was higher than that initiated by BPO. Addition of maleic anhydride increased the encapsulating ratio and the stable encapsulating ratio of encapsulated nano‐CaCO₃. For the encapsulated nano‐CaCO₃ prepared in methanol–water, the diameter of the encapsulated nano‐CaCO₃ particle increased from 60–70 nm to about 100 nm and the morphology changed from a cube with a sharp edge to spherical with a rough surface. Copyright © 2006 Society of Chemical Industry