Aqueous colloidal mesoporous nanoparticles with ethenylene-bridged silsesquioxane frameworks with a uniform diameter of ∼20 nm were prepared from bis(triethoxysilyl)ethenylene in a basic aqueous solution containing cationic surfactants. The nanoparticles, which had higher hydrolysis resistance under aqueous conditions, showed lower hemolytic activity toward bovine red blood cells than colloidal mesoporous silica nanoparticles.
Silica-based materials have found many applications in various fields. Alkoxysilanes have been most widely used as precursors. Fine structural control of silica-based materials has become increasingly important for tuning their properties and for developing new functions. In this perspective, utilization of alkoxysilyl groups has been reviewed from the viewpoint of designing siloxane-based nanomaterials. Alkoxy groups have generally been used only as eliminating groups in the sol−gel processing; however, recent research has shown that they are useful for molecular assembly, for generating pores, for linking nanobuiliding blocks, and for selective synthesis of new oligosiloxane compounds.
Siloxane formation reactions of both the nonhydrolytic sol–gel process and Piers–Rubinsztajn reaction can be integrated as Lewis acid promoted siloxane syntheses without involving silanol groups. The former was developed in the field of inorganic materials chemistry and the latter was initiated in polymer chemistry. We have realized both reactions are quite similar, in terms of 1) the nonhydrolytic reaction, 2) the use of alkoxysilanes, 3) the group‐exchange reactions competing with the siloxane formation, and 4) the proposed reaction mechanisms. This Minireview focuses on the above two reactions. The evolution of both reactions should realize a more sophisticated molecular design of siloxane compounds, which surely contributes to the development of advanced functional materials.
Pd/Al2O3 catalysts were prepared using various Al2O3 supports with different structural features such as crystalline phase and crystallinity related to Al3+ coordination, revealing a significant insight on methane (CH4) combustion...
Discrete alkoxysiloxane oligomers were synthesized by nonhydrolytic heterocondensation reactions between alkoxysilanes and chlorosilanes. In their Communication on ff., K. Kuroda and co‐workers show that the combination of the Lewis acid catalyst bismuth trichloride and alkoxysilanes that can form stable carbocations play an important role in the formation of siloxane bonds prior to the occurrence of other competing side reactions. The photograph of bismuth metal was provided by Dr. Ryoji Tanaka.
Beyond silanol: A branched siloxane oligomer bearing terminal dialkoxysilyl groups was nonhydrolytically synthesized by direct alkoxysilylation of a tetraalkoxysilane with a chlorodialkoxysilane in the presence of the Lewis acid BiCl3 (see scheme). The reaction proceeds without the formation of intermediate silanol groups, and provides a selective route for siloxane‐based oligomers.
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