Encapsulation of inorganic particles via miniemulsion polymerization. I. Dispersion of titanium dioxide particles in organic media using OLOA 370 as stabilizer

The dispersion of hydrophilic and hydrophobic titanium dioxide (TiO2) parti cles in organic media (styrene and cyclohexane) was studied to evaluate the effect of dispersion quality (i.e., size and stability) on the encapsulati on efficiencies of subsequent miniemulsion polymerizations. Through screeni ng studies of various block copolymers, OLOA 370 (polybutene-succinimide pe ntamine) was chosen as the stabilizer for detailed dispersion studies on bo th types of TiO2 particles. As a result of strong interactions between the amine end group of the OLOA 370 stabilizer and the hydroxyl groups on the s urface of the hydrophilic TiO2 particles, a good dispersion stability and s mall particle size (D-nu = 39-45 nm) was obtained using 1.0 wt % stabilizer and 20 min of sonification. The dispersions of the hydrophobic TiO2 partic les resulted in a larger average particle size (D-nu = 60 nm) and poorer st ability. (C) 2000 John Wiley & Sons, Inc.