Toward Transparent Nanocomposites Based on Polystyrene Matrix and PMMA-Grafted CeO₂ Nanoparticles

The association of transparent polymer and nanosized pigment particles offers attractive optical materials for various potential and existing applications. However, the particles embedded into polymers scatter light due to refractive index (RI) mismatch and reduce transparency of the resulting composite material. In this study, optical composites based on polystyrene (PS) matrix and poly(methyl methacrylate) (PMMA)-grafted CeO₂ hybrid particles were prepared. CeO₂ nanoparticles with an average diameter of 18 ± 8 nm were precipitated by treating Ce(NO₃)·6H₂O with urea in the presence of a polymerizable surfactant, 3-methacyloxypropyltrimethoxy silane. PMMA chains were grafted on the surface of the nanoparticles upon free radical in situ solution polymerization. While blending of unmodified CeO₂ particles with PS resulted in opaque films, the transparency of the composite films was remarkably enhanced when prepared by PMMA-grafted CeO₂ hybrid particles, particularly those having a PMMA thickness of 9 nm. The improvement in transparency is presumably due to the reduction in RI mismatch between CeO₂ particles and the PS matrix when using PMMA chains at the interface