Preface

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77506/1/1700_ftp.pd

Transformation of sulfur to organic-inorganic hybrids employed by networks and their application for the modulation of refractive indices

In this manuscript, we present the hybrid materials with sulfur as an inorganic element. Initially, the network polymers with the polysulfide-bridged polyhedral oligomeric silsesquioxane were synthesized and mixed with polystyrene and poly(methyl methacrylate). The resulting polymer blends showed higher thermal degradation temperatures than that of the polymer matrix similarly as typical hybrids. Next, it was found that the sulfur-bridging networks can increase refractive indices of the polymer matrices. Moreover, it was revealed that the loss of Abbe numbers was hardly observed by blending to conventional polymers

Preparation of Oleyl Phosphate-Modified TiO 2

TiO2 nanoparticles (NPs) modified with oleyl phosphate were synthesized through stable Ti–O–P bonds and were utilized to prepare poly(methyl methacrylate)- (PMMA-) based hybrid thin films via the ex situ route for investigation of their optical properties. After surface modification of TiO2 NPs with oleyl phosphate, IR and 13C CP/MAS NMR spectroscopy showed the presence of oleyl groups. The solid-state 31P MAS NMR spectrum of the product revealed that the signal due to oleyl phosphate (OP) shifted upon reaction, indicating formation of covalent Ti–O–P bonds. The modified TiO2 NPs could be homogeneously dispersed in toluene, and the median size was 16.1 nm, which is likely to be sufficient to suppress Rayleigh scattering effectively. The TEM images of TiO2/PMMA hybrid thin films also showed a homogeneous dispersion of TiO2 NPs, and they exhibited excellent optical transparency even though the TiO2 content was 20 vol%. The refractive indices of the OP-modified TiO2/PMMA hybrid thin films changed higher with increases in TiO2 volume fraction, and the hybrid thin film with 20 vol% of TiO2 showed the highest refractive index (n = 1.86)

Thermochromism and Structural Change in Polydiacetylenes Including Carboxy and 4‑Carboxyphenyl Groups as the Intermolecular Hydrogen Bond Linkages in the Side Chain

We investigated the thermochromic behavior of polydiacetylenes including the carboxy and 4-carboxyphenyl groups as the side-chain substituents adjacent to the conjugated main chain, and then, the thermal stability and the thermochromism reversibility of the polymers were related to changes in the polymer conformations monitored by IR and Raman spectroscopies and powder X-ray diffractions. The polydiacetylenes with no or a phenylene spacer between the main chain and the carboxylic acid moiety were revealed to exhibit a thermal resistance for maintaining reversible thermochromism in a high temperature range, rather than polydiacetylenes with a conventional structure with a flexible alkylene spacer. The molecular stacking structures of the diacetylenes and the corresponding polymers in the crystals were discussed based on the results of an X-ray single-crystal structure analysis as well as the powder X-ray diffraction measurements

Investigation of photoluminescence of Si−O−C(−H) ceramics at an early stage of decarbonization by using high energy excitation

Si−O−C(−H) ceramics with reduced carbon contents were prepared by pyrolyzing polysiloxane particles in hydrogen at temperatures of 750, 800 and 850 °C. Under HeCd laser irradiation (325 nm), the obtained ceramics show broad spectra peaking at 400–415 nm. On the other hand, the excitation on the higher energy region by an ArF excimer laser (193 nm) induces new PL bands located at short wavelength region of 300 and 355 nm. Such high energy PL bands appear prominently in the ceramics synthesized at 750 °C, and are minor in ceramics synthesized at 800 and 850 °C

Polysilsesquioxanes for Gate-Insulating Materials of Organic Thin-Film Transistors

Printable organic thin-film transistor (O-TFT) is one of the most recognized technical issues nowadays. Our recent progress on the formation of organic-inorganic hybrid thin films consists of polymethylsilsesquioxane (PMSQ), and its applications for the gate-insulating layer of O-TFTs are introduced in this paper. PMSQ synthesized in toluene solution with formic acid catalyst exhibited the electric resistivity of higher than 1014 Ω cm after thermal treatment at 150°C, and the very low concentration of residual silanol groups in PMSQ was confirmed. The PMSQ film contains no mobile ionic impurities, and this is also important property for the practical use for the gate-insulating materials. In the case of top-contact type TFT using poly(3-hexylthiophene) (P3HT) with PMSQ gate-insulating layer, the device properties were comparable with the TFTs having thermally grown SiO2 gate-insulating layer. The feasibility of PMSQ as a gate-insulating material for O-TFTs, which was fabricated on a flexible plastic substrate, has been demonstrated. Moreover, by the modification of PMSQ, further functionalities, such as surface hydrophobicity, high permittivity that allows low driving voltage, and photocurability that allows photolithography, could be appended to the PMSQ gate-insulating layers