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491.
Iwamoto T Sato K Ishida S Kabuto C Kira M 《Journal of the American Chemical Society》2006,128(51):16914-16920
The first dialkyl-substituted silicon-chalcogen doubly bonded compounds [R2Si=X; R2=1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl, X = S (4), Se (5), and Te (6)]were synthesized by the reactions of an isolable dialkylsilylene R2Si: (3) with phosphine sulfide, elemental selenium, and elemental tellurium, respectively. Systematic changes of characteristics of silicon-chalcogen double bonds are elucidated by X-ray analysis, UV-vis spectroscopy, and DFT calculations. In the solid state, the unsaturated silicon atom in 4-6 adopts planar geometry and the extent of the shortening of Si=X double bonds from the corresponding Si-X single bonds decreases in the order 4 > 5 > 6. In the absorption spectra of 4-6, pi -->pi* transition bands are observed distinctly in addition to n -->pi* transition bands. Both the n -->pi* and pi -->pi* transitions are red-shifted in the order 4 < 5 < 6, and the difference between the energies of the two transitions is kept almost constant among 4-6. The tendency is explained using the qualitative perturbation theory and is reproduced by the DFT calculations for model silanechalcogenones. Addition reactions of water, methanol, and isoprene to 4-6 are reported. 相似文献
492.
Hideki Sugimoto Kazunori Nunome Kazuki Daimatsu Eiji Nakanishi Katsuhiro Inomata 《Colloid and polymer science》2010,288(10-11):1131-1138
The aim of this study was to prepare transparent nanohybrid films with low coefficient of thermal expansion (low CTE), which consist of acryl resin and nanosized clay. The hybrid films with different clay contents were prepared by UV curing of tricyclodecane dimethanol diacrylate (TCDDMDA) including nanosized clay. All obtained films were transparent similar to pure poly(TCDDMDA). In addition, the film containing 40 wt.% of clay showed a low CTE of 10 ppm/K in 150–200 °C, which is similar to that of inorganic materials such as glass. The significant property improvement is related to shape effect and orientation of clay in polymer matrix. Wide-angle X-ray diffraction measurement was carried out to investigate orientation of nanosized clay in polymer matrix. From this measurement, it was confirmed that the clay platelets were oriented parallel with film surface with increasing clay content, and orientation coefficient of the clay in polymer matrix reached to f?=?0.65 for the hybrid film containing 40 wt.% of clay. Though, in comparison with the matrix, the flexibility of the hybrid film evaluated by the wind roll test with steel bar was lowered by increase of clay content, the hybrid film containing 40 wt.% of clay could be rewound with steel bar 10 mm across, and its flexibility was retained. 相似文献
493.
Mami Miyairi Dr. Tsuyoshi Taniguchi Dr. Tatsuya Nishimura Prof. Katsuhiro Maeda 《Angewandte Chemie (International ed. in English)》2023,62(37):e202302332
Improved methods for the synthesis of linear and cyclic poly(diphenylacetylene)s by polymerization of the corresponding diphenylacetylenes using MoCl5- and WCl4-based catalytic systems have been developed. MoCl5 induces migratory insertion polymerization of diphenylacetylenes in the presence of arylation reagents such as Ph4Sn and ArSnnBu3 to produce cis-stereoregular linear poly(diphenylacetyelene)s with high molecular weights (number-average molar mass (Mn)=30,000–3,200,000) in good yields (up to 98 %). On the other hand, WCl4 induces ring expansion polymerization of diphenylacetylenes in the presence of Ph4Sn or reducing reagents to produce cis-stereoregular cyclic poly(diphenylacetylene)s with high molecular weights (Mn=20,000–250,000) in moderate to good yields (up to 90 %). Both catalytic systems are applicable to the polymerization of various diphenylacetylenes having polar functional groups such as esters that are not efficiently polymerized by conventional methods using WCl6-Ph4Sn and TaCl5-nBu4Sn systems. 相似文献
494.
Optical Review - We propose an imaging method using commercially available profile sensor. Specifically, we use a multipixel CMOS area sensor capable of acquiring projection profiles and perform... 相似文献
495.
Unique macromolecular helicity inversion of stereoregular, optically active poly(phenylacetylene) derivatives induced by external achiral and chiral stimuli is briefly reviewed. Stereoregular, cis-transoidal poly(phenylacetylene)s bearing an optically active substituent, such as (1R,2S)-norephedrine (poly- 1 ) and β-cyclodextrin residues (poly- 2 ), show an induced circular dichroism (ICD) in the UV-visible region of the polymer backbone in solution due to a predominantly one-handed helical conformation of the polymers. However, poly- 1 undergoes a helix-helix transition upon complexation with chiral acids having an R configuration, and the complexes exhibit a dramatic change in the ICD of poly- 1 . Poly- 2 also shows the inversion of macromolecular helicity responding to molecular and chiral recognition events that occurred at the remote cyclodextrin residues from the polymer backbone; the helicity inversion is accompanied by a visible color change. A similar helix-helix transition of poly((R)- or (S)-(4-((1-(1-naphthyl)ethyl)carbamoyl)phenyl)acetylene) is also briefly described. 相似文献
496.