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

Abstract

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-co-PMPM) 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 promising light stabilizers with covalent functionalization of polymeric HALS, which has little photocatalytic activity, and can be introduced into the weathering-resistant polymer materials to improve their application properties.