TiO2-SiO2 composite nanoparticles containing hindered amine light stabilizers encapsulated by MMA-PMPM copolymers

TiO2-SiO2 composite nanoparticles containing hindered amine light stabilizers (HALSs) were prepared by encapsulation of commercially available TiO2-SiO2 nanoparticles using methyl methacrylate (MMA) and 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate (PMPM) copolymers through mini-emulsion polymerization. The Fourier transform infrared spectral analysis (FTIR) showed that the hindered amine light stabilizer PMPM was incorporated into the TiO2-SiO2/P(MMA-co-PMPM) composite nanoparticles. The X-ray photoelectron spectroscopy analysis (XPS) showed that the surface of TiO2-SiO2 nanoparticles was enriched with HALS moieties. The formation of P(MMA-co-PMPM) random copolymers on the surface of TiO2-SiO2 nanoparticles was determined by differential scanning calorimetry (DSC), and the percentage of the chemically grafted P(MMA-co-PMPM) coverage on the TiO2-SiO2 nanoparticles surface was 40.9 wt% determined by thermogravimetric analysis (TGA), which revealed that the TiO2-SiO2 nanoparticles were successfully encapsulated by MMA-PMPM copolymers. Scanning electron microscopy analysis indicated that the TiO2-SiO2/P(MMA-coPMPM) composite nanoparticles were mainly homogeneous spherical shape particles, with an average size of about 90 nm. Rhodamine B (Rh. B) photocatalytic degradation study revealed UV-shielding characteristics for TiO2-SiO2/P(MMA-co-PMPM) composite nanoparticles and showed a remarkable decrease in photocatalytic activity of TiO2-SiO2 nanoparticles. These results indicated that TiO2-SiO2/P(MMA-co-PMPM) composite nanoparticles may be