Polysilsesquioxanes can be regarded as organic－inorganic hybrid materials in a molecular level. We can readily tune the properties of the materials for realizing the desired ones by changing the contents or types of organic components. In advance, the hierarchical structures have potentials for generating further characteristics distinctly different from those of the constituents. From this viewpoint, polyhedral oligomeric silsesquioxanes (POSS) are attractive as a cornerstone in highordered materials. Herein, we review recent studies about octa-substituted POSS-based functional materials and specifi cally explain the design concepts for applying the signifi cant characteristics of POSS for the material properties. In the former parts, we introduce the examples concerning the POSS fi llers for improving thermal stability and modulating the refractive indices of the matrices. We will also mention about the recent study on the POSS-based ionic liquid. In the latter parts, we describe the application of POSS-based materials in aqueous media. Particularly, we explain the upconversion system of the light energy in water and the advanced MRI contrast agents based on the water-soluble POSS materials.

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SynopsisThe synthesis and characterization of epoxy/silica hybrids are reviewed based on our recent works. We synthesized epoxy/silica hybrids through the in situ polymerization of silane alkoxide in the epoxy curing process. The hybrids obtained through this in situ process exhibit no clear glass transition phenomenon and have high surface hardness and low refractive index. The epoxy/silica hybrids were also prepared from the epoxy resin with silsesquioxane backbone moiety. This type of hybrids has low dielectric constant and low refractive index because of their high free volume fraction.

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SynopsisThe preparation of organic－inorganic hybrid gate insulating materials of poly(methyl silsesquioxane) (PMSQ) at a low processing temperature has been studied for use in organic thin fi lm transistors (O-TFTs) by the solution process. It is found that the electrical resistivity of a PMSQ fi lm synthesized by a sol－gel method is signifi cantly infl uenced by the synthesis conditions such as organic solvent and reaction procedure. PMSQ fi lms prepared in toluene show a high resistivity of over 10¹⁴Ωcm even at a low thermal treatment of 150°C, which is attributed to the decrease in the silanol concentration of the PMSQ fi lms. PMSQ had low leakage current derived from less mobile ionic impurities, which is an essential factor for gate insulating materials. Top-contact O-TFT fabricated on a PMSQ gate insulator using poly(3-hexylthiophene) (P3HT) exhibits mobility improvement similarly to devices with self-assembled monolayer-modified SiO₂ insulating materials.The chemical modification of PMSQ could be provided higher dielectric constants for low driving voltage and photofunctionality for photolithographic properties.

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[in Japanese]

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SynopsisDevelopment of a new series of self-assembling lithographic materials based on polyhedral oligomeric silsesquioxane(POSS) containing block copolymers was achieved. The POSS-containing diblock copolymer of PMMA-b-PMAPOSS was successfully synthesized via living anionic polymerization technique. Thin fi lms were prepared by spin-cast from the polymer solution on silicon wafers and subsequent solvent annealing. Dot-like nanostructures were successfully obtained in the thin fi lms. A long-range nanostructure ordering in the resulting thin fi lms was achieved by using two kinds of Directed Self-Assembly of PMMA-b-PMAPOSS.

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SynopsisCompounds with π-electron systems linked by an organosilicon unit are of current interest, because of their use, such as for emissive and carrier-transporting materials. The author and coworkers have reported the potential applications of polymers having silicon-linked oligothiophene units as hole-transporting materials of organic EL devices. Recently, these types of the compounds were found to be usable as active components of organic FETs (fi eld eff ect transistors). Of these, star-shaped compounds with three oligothiophene groups linked by an organosilicon core showed high FET activity with the maximum mobility of 0.064 cm²/Vs.It was also demonstrated that polymers composed of alternating oligothiophene and disilane units readily underwent reactions with TiO₂ surface under UV irradiation to form polymer-attached TiO₂ electrodes that were applicable to DSSCs (dye-sensitized solar cells). Interestingly, the polymers formed hybrid materials with SWNT (single-wall carbon nanotube) by ball-milling and the resulting hybrids also were applied to DSSCs, leading to enhanced power conversion efficiency as compared with that without SWNT.

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