a1 Department of Nano-structured & Advanced Materials, Graduate School of Science and Engineering, Kagoshima University, Kagoshima 890-0065, Japan
a2 Advanced Materials Laboratory, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan
a3 Department of Fine Materials Engineering, Faculty of Textile Science and Technology, Shinshu University, Ueda 386-8567, Japan
A series of water-soluble silicon oxide materials was synthesized by the sol-gel reaction of tetramethoxysilane (TMOS)/3-aminopropyltrimethoxysilane (APTMOS) mixtures catalyzed by hydrochloric acid with varying TMOS/APTMOS ratios. Increase in TMOS composition made the products less water-soluble, and the richest TMOS composition for the water-soluble silicon oxide materials was found to be TMOS/APTMOS = 7/3 (mol/mol). Ultraviolet-visible spectroscopy of a 10 wt% aqueous solution of the product with TMOS/APTMOS = 7/3 showed a high transmittance in the visible region. Its infrared spectrum showed an absorptionband attributable to the Si–O bond, and the 29Si dipole decoupled/magic angle spinning–nuclear magnetic resonance spectrum exhibited signals in the regions of T3, Q3, and Q4, indicating a dense siloxane network structure. A peak due to an ordered structure with a 1.76 nm periodicity was observed in the x-ray diffraction profile, and a stripe pattern was observed in the transmission electron microscopy image. These results indicate that the rodlike silicon oxide macromolecules with a 1–2-nm diameter stack parallel. Thus a silicon oxide material with nano-ordered structure was successfully formed and such a structure produced the water solubility.
(Received February 16 2005)
(Accepted May 02 2005)
(Online publication August 2005)