To improve the photoluminescence and long-term stability of the Y2O2S:Eu3+ phosphor, surface coatings with silica nanoparticles and poly(methyl methacrylate) (PMMA)-silica nanocomposites were performed via four different techniques. Phosphors were coated with nearly monodispersed silica nanoparticles (5 nm) by a dip-coating method and a sol−gel method (Stöber method). To fabricate the silica nanopariticles used for the phosphor coating, hydrolysis and condensation reactions for the formation of silica nanoparticles, and radical polymerization for the formation of poly(1-vinyl-2-pyrrolidone) were performed simultaneously. Phosphors were coated with PMMA-silica nanocomposites by using two different methods: by reacting silica nanoparticles and methyl methacrylate (MMA) monomer and by reacting mixtures containing MMA and tetraethylorthosilicate. Between these methods, the latter method exhibited the greatest enhancement of photoluminescence and long-term stability of the phosphors. When phosphors were coated with PMMA-silica nanocomposite by the second method, the PL intensity of Y2O2S:Eu3+ was enhanced approximately 5% over that of the uncoated phosphors. In contrast to a decrease in cathode luminescence (CL) intensity with increasing bombardment time for uncoated phosphor, a nearly constant CL intensity was observed for the phosphors coated with PMMA-silica nanocomposite by the latter method.

To fabricate dental nanocomposites containing finely dispersed silica nanoparticles, nearly monodispersed silica nanoparticles smaller than 25 nm were synthesized without forming any aggregates via a modified solgel process. Since silica nanoparticles synthesized by the Stober method formed aggregates when the particle size is smaller than 25 nm, the synthetic method was modified by changing the reaction temperature and adding poly(1-vinyl-2-pyrrolidinone) (PVP) to the reaction mixture. The size of the formed silica nanoparticles was reduced by increasing the reaction temperature or adding PVP. Furthermore, the formation of aggregates with primary silica nanoparticles smaller than 25 nm was prevented by increasing the amount of PVP added to the reaction mixture. To enhance the dispersion of the silica particles in an organic matrix, the synthesized silica nanoparticles were treated with 3-methacryloxypropyltrimethoxysilane (γ-MPS). A dental nanocomposite containing finely dispersed silica nanoparticles could be produced by using the surface-treated silica nanoparticles.

To enhance the heat resistance of poly(styrene‐co‐acrylonitrile‐co‐butadiene), ABS, miscibility of poly(styrene‐co‐acrylonitrile), SAN, with poly(styrene‐co‐n‐phenyl maleimide), SNPMI, having a higher glass transition temperature than SAN was explored. SAN/SNPMI blends casted from solvent were immiscible regardless of copolymer compositions. However, SNPMI copolymer forms homogeneous mixtures with SAN copolymer within specific ranges of copolymer composition upon heating caused by upper critical solution temperature, UCST, type phase behavior. Since immiscibility of solvent casting samples can be driven by solvent effects even though SAN/SNPMI blends are miscible, UCST‐type phase behavior was confirmed by exploring phase reversibility. When copolymer composition of SNPMI was fixed, the phase homogenization temperature of SAN/SNPMI blends was increased as AN content in SAN copolymer increased. To understand the observed phase behavior of SAN/SNPMI blend, interaction energies of blends were calculated from the UCST‐type phase boundaries by using the lattice‐fluid theory combined with a binary interaction model. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1131–1139, 2008