Polymer encapsulation of TiO 2 by seeded emulsion polymerization to improve the dispersion stability and reflectance

Submicron-sized Al2O3(Al)-coated titanium dioxide (Al-TiO2) particles were directly encapsulated via seeded emulsion (co)polymerization of methyl methacrylate (MMA) and (methyl methacrylate-co- hydroxyethyl methacrylate) (MMA-co-HEMA) having shell thickness 10–35 nm. Polymer encapsulation significantly improved the dispersion stability of Al-TiO2 particles in both polar (water) and nonpolar (toluene) media compared to unencapsulated Al-TiO2, however, the molar ratio of monomers (MMA/ HEMA) affected the dispersion stability in course of time duration. The poly(MMA)-coated Al-TiO2 showed the highest dispersion stability and a good dispersibility in toluene compared to poly(MMA-co- HEMA) coating due to the more hydrophobic nature, whereas poly(MMA-co-HEMA)-coated particles at molar ratio 90/10 provided better dispersion stability in aqueous media at our experimental conditions. Polymer encapsulation increased the reflectance or hiding power of Al-TiO2 at visible wavelengths to some extent despite the use of low refractive index materials (MMA or/and HEMA) as a shell.

• Research Project