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71.
Synthesis of thermally stable aromatic poly(spiroorthocarbonate)s having a Cardo or bent structure
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Masaki Moritsugu Ryota Seto Kozo Matsumoto Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2016,54(10):1409-1416
Novel poly(spiroorthocarbonate)s [poly(SOC)]s having a Cardo or bent structure were synthesized by polycondensation of several bis‐catechols having fluorene (BCFL), spirobisindane (BCSPI), or spirobischromane (BCSPC) in the structure with 2,2,6,6‐tetrachlorobenzo[1,2‐d:4,5‐d’]bis[1,3]dioxole (4ClBD). Synthesis of poly(SOC)s was confirmed by NMR and IR spectrometry. The poly(SOC)s obtained from BCFL or BCSPC were soluble in common organic solvents. The glass transition temperature of the poly(SOC)s was not detected by differential scanning calorimetry (DSC) in the range of 50–300 °C. The 10 wt % decomposition temperature of the poly(SOC)s was found to be above 400 °C. These results indicated the high thermal stability of the poly(SOC)s. Soluble poly(SOC)s could be possessed to form a film on a glass plate by the spin coat method. The obtained polymer films were 0.2 μm in thickness with 95% light transmission in the optical wavelength range. These results suggested that the Cardo or bent structure may block the packing of the main‐chain of the structure, which improves the solubility of the polymers, increases transparency, and enhances the thermal stability of SOCs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1409‐1416 相似文献
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T. Nakajima-KambeN.G. Edwinoliver H. MaedaK. Thirunavukarasu M.K. GowthamanK. Masaki S. MahalingamN.R. Kamini 《Polymer Degradation and Stability》2012,97(2):139-144
A lipase from Aspergillus niger MTCC 2594 was purified 53.8-fold to homogeneity by hydrophobic interaction chromatography using octyl sepharose and the enzyme showed two protein bands with apparent molecular mass of 35 and 37 kDa respectively. The lipase exhibited maximum activity at pH 7.0 and 37 °C and was stable between pH 4.0 and 10.0 and temperatures up to 50 °C. The values of Km and Vmax were 3.83 mM and 32.21 μmol/min/mg respectively, using olive oil as substrate. Lipase encoding gene, lipA, coded for 297 amino acid residues with conserved pentapeptide sequence, G-H-S-L-G, was cloned and expressed in Pichia pastoris. Although lipA showed high homology with the known Aspergillus lipases, it exhibited differences in putative lid domain. Both native and recombinant lipases have potential for degradation of poly(lactic acid) and poly(ε-caprolactone), and the present study will serve as a baseline of initial studies for its exploitation in polymer degradation. 相似文献
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Mitsuji Yamashita Lakonda Nagaprasada Rao Valluru Krishna Reddy Motoki Maeda Tatsuo Oshikawa Masaki Takahashi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1661-1665
Novel pentofuranose analogs of phospha sugar derivatives were synthesized starting from 1-phenyl-2-phospholene 1-oxide ( 1 ). First, the allylic oxidation of 1-phenyl-2-phospholene 1-oxide ( 1 ) with CrO 3 in Ac 2 O-AcOH or 3-hydroxy-1-phenyl-2-phospholene ( 2 ) with MnO 2 afforded 1-phenyl-4-oxo-2-phospholene 1-oxide ( 3 ). The C-5 alkylation of 3 in the presence of NaH by using benzyl bromide or methyl iodide as electrophiles afforded the target title compounds. 相似文献
77.
Takaaki Taguchi Masaki Yabe Hitomi Odaki Miki Shinozaki Mikko Metsä-Ketelä Takao Arai Susumu Okamoto Koji Ichinose 《Chemistry & biology》2013,20(4):510-520
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78.
Makoto Kunisada Taro Masaki Ryusuke Ono Hironobu Morinaga Eiji Nakano Flandiana Yogianti Kunihiro Okunishi Hiroshi Sugiyama Chikako Nishigori 《Photochemistry and photobiology》2013,89(3):649-654
The UVA is currently thought to be carcinogenic because, similar to UVB, it induces the formation of cyclobutane pyrimidine dimers (CPDs). Various drugs have been reported to cause photosensitive drug eruptions as an adverse effect. Although the precise mechanism of photosensitive drug eruption remains to be elucidated, it is generally accepted that free radicals and other reactive molecules generated via UV‐irradiated drugs play important roles in the pathogenesis of photosensitive drug eruptions. The waveband of concern for photo‐reactive drugs is UVA‐visible light, but some extend into the UVB region. We tested whether photosensitive drugs could enhance CPD formation after UVA exposure by using isolated DNA in the presence of several reported photosensitive drugs using high‐performance liquid chromatography. We found that the diuretic agent hydrochlorothiazide (HCT) significantly enhanced the production of TT dimers over a wide range of UVA. Furthermore, we investigated whether UVA plus HCT could enhance CPD production in xeroderma pigmentosum model mice defective in nucleotide excision repair. Immunofluorescence studies showed that CPD formation in the skin significantly increased after 365 nm narrow‐band UVA irradiation in the presence of HCT, compared with that in wild‐type mice. HCT could be used with caution because of its enhancement of UVA‐induced DNA damage. 相似文献
79.
Xingzhong Guo Wenyan Li Hui Yang Kazuyoshi Kanamori Yang Zhu Kazuki Nakanishi 《Journal of Sol-Gel Science and Technology》2013,67(2):406-413
An in situ two-step processing using an initial acid catalysis step accompanied by an epoxide-mediated condensation step in the presence of ammonium chloride (NH4Cl) is reported, and macroporous cocontinuous methylsilsesquioxane (MSQ) monoliths have been successfully prepared by this processing. We explain the hydrolysis, gelation behavior and phase separation of MTMS(methyltrimethoxysilane)-MeOH(methanol)-HCl-PO(propylene oxide) system and the in situ effect of NH4Cl, and examine the macroporous morphology and pore structures of MSQ monoliths obtained under different conditions. Macroporous MSQ monolith under optimized conditions possesses a narrow macropore size distribution between 3 to 10 μm, surface area as high as 366 m2·g?1 and minimal shrinkage of only 1 %. 相似文献
80.
Takuya Sawaki Dr. Tomoya Ishizuka Prof. Dr. Masaki Kawano Dr. Yoshihito Shiota Prof. Dr. Kazunari Yoshizawa Prof. Dr. Takahiko Kojima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(27):8978-8990
The thermal and photochemical reactions of a newly synthesized complex, [RuII(TPA)(tpphz)]2+ ( 1 ; TPA=tris(2‐pyridylmethyl)amine, tpphz=tetrapyrido[3,2‐a:2′,3′‐c:3′′,2′′‐h: 2′′′,3′′′‐j]phenazine), and its derivatives have been investigated. Heating a solution of complex 1 (closed form) and its derivatives in MeCN caused the partial dissociation of one pyridylmethyl moiety of the TPA ligand and the resulting vacant site on the RuII center was occupied by a molecule of MeCN from the solvent to give a dissociated complex, [RuII(η3‐TPA)(tpphz)(MeCN)]2+ ( 1′ , open form), and its derivatives, respectively, in quantitative yields. The thermal dissociation reactions were investigated on the basis of kinetics analysis, which indicated that the reactions proceeded through a seven‐coordinate transition state. Although the backwards reaction was induced by photoirradiation of the MLCT absorption bands, the photoreaction of complex 1′ reached a photostationary state between complexes 1 and 1′ and, hence, the recovery of complex 1 from complex 1′ was 67 %. Upon protonation of complex 1 at the vacant site of the tpphz ligand, the efficiency of the photoinduced recovery of complex 1 +H+ from complex 1′ +H+ improved to 83 %. In contrast, dinuclear μ‐tpphz complexes 2 and 3 , which contained the RuII(TPA)(tpphz) unit and either a RuII(bpy)2 or PdIICl2 moiety on the other coordination edge of the tpphz ligand, exhibited 100 % photoconversion from their open forms into their closed forms ( 2′ → 2 and 3′ → 3 ). These results are the first examples of the complete photochromic structural change of a transition‐metal complex, as represented by complete interconversion between its open and closed forms. Scrutinization by performing optical and electrochemical measurements allowed us to propose a rationale for how metal coordination at the vacant site of the tpphz ligand improves the efficiency of photoconversion from the open form into the closed form. It is essential to lower the energy level of the triplet metal‐to‐ligand charge‐transfer excited state (3MLCT*) of the closed form relative to that of the triplet metal‐centered excited state (3MC*) by metal coordination. This energy‐level manipulation hinders the transition from the 3MLCT* state into the 3MC* state in the closed form to block the partial photodissociation of the TPA ligand. 相似文献