Optical Properties of Double-Decker-Shaped Poly (Silsesquioxane)
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1056-HH06-05
Optical Properties of Double-Decker-Shaped Poly (Silsesquioxane) Akira Watanabe, Shohei Tadenuma, and Tokuji Miyashita Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 9808577, Japan ABSTRACT The double-decker-shaped silsesquioxane (DDSQ) is a new family of silsesquioxanes consisting of a Si-O-Si case structure and functional organic side chains. The optical properties of a novel organic-inorganic hybrid polymer based on the DDSQ were studied. The doubledecker-shaped poly(silsesquioxane) (DDPSQ) showed excellent transparency and thermal stability. The thermo-optic coefficient of the DDPSQ is 3 or 4 times larger than conventional polymers. INTRODUCTION The POSS (polyhedral oligomeric silsesquioxane) has a nanometer-sized silica-like cage structure functionalized with various kinds of organic groups. The double-decker-shaped silsesquioxane (DDSQ) is a new family of silsesquioxanes consisting of a Si-O-Si case structure and functional organic side chains. The DDSQ has two siloxane rings connected in the shape of double-decker. The DDSQ is obtained as a sodium silanolate by the hydrolysis and the condensation of the phenyltrimethoxysilane [1]. Using the sodium silanolate of the DDSQ as s starting material, various kinds of DDSQs with reactive substituents can be synthesized as shown in Figure 1 [1-3]. For example, open and close-cage hydrosilane compounds, closed-cage vinyl compound, open-cage silanol compound, and so on.
Figure 1. Various double-decker-shaped silsesquioxanes. (a) open-cage hydrosilane, (b) closed-cage hydrosilane, (c) closed-cage vinyl, and (d) open-cage silanol compounds.
The DDSQ as a building block provides elegant designs and the controllable reaction for organic-inorganic hybrid materials. The hybridization between organic and inorganic moieties can be controlled by the chemical reaction of the functionalized DDSQ. In this study, we report
the optical properties of a novel organic-inorganic hybrid polymer based on the DDSQ. One of the possible application fields of the thermally stable and optically transparent double-deckershaped poly(silsesquioxane) (DDPSQ) is a thermo-optic switch which needs a large thermo-optic (TO) coefficient dn/dt and thermal stability. Inorganic silica is highly-thermally-stable but the TO coefficient is low. Therefore, TO switches fabricated of silica-based waveguide materials require large driving power. On the other hand, the TO coefficient for some polymers are one order of magnitude larger than those for inorganic glasses. However, the problem is the thermal stability of the polymers. In this paper, we studied the TO effect of the DDPSQ having an excellent transparency and thermal stability. EXPERIMENT The DDPSQ was synthesized by the hydrosilylation reaction between a hydrosilanefunctionalized DDSQ and a vinyl-functionalized DDSQ with a Pt catalyst. The polymers were spin-coated on a Si substrate, and then heat-treated at 250oC for 1 hr. The refractive index n and the TO coefficient were measured by spectro
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