Remarkable Birefringence in a TiO2鈥揝iO2 Composite Film with an Aligned Mesoporous Structure

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• 作者：Hirokatsu Miyata ; Yuta Fukushima ; Kohei Okamoto ; Masahiko Takahashi ; Masatoshi Watanabe ; Wataru Kubo ; Atsushi Komoto ; Shin Kitamura ; Yosuke Kanno ; Kazuyuki Kuroda
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：August 31, 2011
• 年：2011
• 卷：133
• 期：34
• 页码：13539-13544
• 全文大小：842K
• 年卷期：v.133,no.34(August 31, 2011)
• ISSN：1520-5126

文摘

Mesoporous titania鈥搒ilica composite films with highly aligned cylindrical pores are prepared by the sol鈥揼el method using a substrate with structural anisotropy. The strong alignment effect of a rubbing-treated polyimide film on a substrate provides a narrow alignment distribution in the plane of the film regardless of the fast condensation rate of titania precursors. The collapse of the mesostructure upon the surfactant removal is effectively suppressed by the reinforcement of the pore walls with silica by exposing the as-deposited film to a vapor of a silicon alkoxide. The existence of a silica layer on the titania pore wall is proved from the distributions of Ti and Si estimated by the elemental analysis in high resolution electron microscopy. The obtained mesoporous titania鈥搒ilica composite film exhibits a remarkable birefringence reflecting the highly anisotropic mesoporous structure and the high refractive index of titania that forms the pore wall. The 螖n value estimated from the optical retardation and the film thickness is larger than 0.06, which cannot be achieved with the conventional mesoporous silica films with uniaxially aligned mesoporous structure even though the alignment of the pores in the films is perfect. These inorganic films with mesoscopic structural anisotropy will find many applications in the field of optics as phase plates with high thermal/chemical/mechanical stabilities.