IntroductionIn recent years, organic-inorganic nanometer-composites have attracted great interest to researchers since they frequently exhibit unexpected hybrid properties synergistically derived from the two components. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] One of the most promising composite system would be hybrids based on organic polymers and inorganic clay minerals consisting of silicate layers [4][5][6][7][8][9][10][11][12][13][14][15][16][17] . In our previous works, we have synthesized nylon 6-clay hybrid (NCH) in which 1 nm thick silicate layers of clay minerals are exfoliated and homogeneously dispersed in the nylon 6 matrix. [5] The NCH exhibits various superior properties such as high strength, high modulus, and high heat resistance, compared to conventional nylon 6. [6] Since then, other polymer-clay hybrids such as polyimide, [7] epoxy resin, [8] polystyrene, [9] polycaprolactone, [10] acrylic polymer, [11] polyurethane, [12] and poly(ethylene terephthalate) [13] were reported. However, the dispersion of exfoliated silicates was achieved only in a few cases, i. e., nylon, [5,6] polyimide, [7] epoxy resin, [8] and polystyrene. [9 d, e] Polyolefins, i. e., poly(propylene) (PP), polyethylene (PE), ethylene-propylene rubber (EPR), are the most widely used polymers. However, there was few report of polyolefin-clay hybrids in which the silicate layers were exfoliated and homogeneously dispersed. It has been considered that the silicate layers of the clay have high polarity and are incompatible with polyolefins. Coates [14] and Mülhaupt [15] independently reported the in-situ olefin polymerization in the existence of organophilic clay to afford polyolefin-clay nanocomposites wherein the polyolefins were intercalated into the clay galleries. Recently, we have found polyolefin oligomers with polar functionality were intercalated into the organophilic clay galleries during melt-blending and these phenomena were the key to achieve the dispersion of exfoliated silicates in polyolefins. [16] We reported that PP and organophilic clay were melt-blended in the presence of maleic anhydride modified PP oligomer to obtained PP-clay hybrids wherein a large fraction of the clay silicates were found to be exfoliated. Since then, this system using modified PP oligomers as the compatibilizer was investigated by many researchers. [17] In this study we report a novel and general approach to prepare polyolefin-clay hybrids by using organophilic clay and maleic anhydride modified polyolefins during melt-blending and examine the morphologies and the basic properties of the hybrids. Results and discussionAll samples of polyolefin-clay hybrids were prepared by melt-blending maleic anhydride modified polyolefins and organophilic clay above each melting point. On the Full Paper: A novel and general approach to prepare polyolefin-clay hybrids by using the maleic anhydride modified polyolefins and organophilic clay during meltblending was reported. The silicate layers of the clay were exfoliated and homogen...
Polyethylene-clay hybrids have been prepared successfully by melt compounding with maleic anhydride grafted polyethylene (MA-g-PE), organophilic clay and polyethylene. In these polyethylene-clay hybrids, the silicate layers of the clay were exfoliated and dispersed to the monolayers. The hybrids exhibit higher tensile yield strengths and tensile moduli than those of polyethylene matrices and those of polyethylene-inorganic clay composites. When the 5-wtOh clays were loaded, the tensile yield strength and the tensile modulus of the hybrid were, respectively, 1.4 and 1.8 times higher than those of the polyethylene/MA-g-PE mixture. The gas permeability of that clay hybrid decreased 30% compared with polyethylene/MA-g-PE mixture.
We have demonstrated that polystyrene latex coated with titania nanosheets can be fabricated into a close-packed colloidal crystalline array, and that these coated colloidal spheres can be used to control the peak position of optical stop bands through the coating. The titania-nanosheets-coated polystyrene latex was prepared by the layer-by-layer (LBL) assembly coating process, involving alternating lamination of cationic polyelectrolytes and anionic titania nanosheets on monodisperse polystyrene latex particles. The Bragg diffraction peak of the colloidal crystalline array shifted to longer wavelengths with the coating of titania nanosheets. This red shift was caused by an increase in refractive index upon coating, as revealed by angle-resolved reflection spectra measurements. The current work suggests new possibilities for the creation of advanced colloidal crystals having tunable optical properties from tailored colloidal spheres.
Titania coated monodisperse silica spheres have been synthesized and fabricated as a close-packed colloidal crystalline array. We have demonstrated that the coated colloidal sphere can be used to control the peak position of the optical stop band through variation of the coating thickness. The titania coated silica spheres were prepared by the layer-by-layer assembly coating process, which reciprocally laminates the cationic polyelectrolyte and the anionic titania nanosheets on a monodisperse silica spheres, and were sintered to change the titania nanosheets to anatase. The Bragg diffraction peak of the colloidal crystalline array shifted to the long wavelength region with an increase of thickness of the titania layer. Angle-resolved reflection spectra measurements clarified that the red shift was caused by increasing of the refractive index with increase of the thickness of the layer. The current work suggests new possibilities for the creation of advanced colloidal crystalline arrays with tunable optical properties from tailored colloidal spheres.
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