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S. D. Morse T. D. Wilson C. I. Merrill 《Journal of polymer science. Part A, Polymer chemistry》1984,22(3):645-656
The acid-catalyzed polymerization of epichlorohydrin was modified by the addition of 1,4-butanediol diglycidyl ether to the reaction. The amount of diepoxide added and the method of addition were varied to produce a series of polymers with increased molecular weight, broad molecular weight distributions, and variations in hydroxyl functionality. Polyurethane networks were prepared from these polyols for the evaluation of elastomeric properties. The most obvious result was the lack of elastomeric network formation in the unmodified material when modified polyols produced elastomeric properties under the same conditions. Differences in properties between samples with more diepoxide added in the original polymerization generally showed trends to lower elongation and higher modulus. Changes in the method of addition of the diepoxide produced great differences in the toughness of the elastomers formed in the cure process. 相似文献
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Absorption and emission spectral studies of M(CO)4L complexes (M = Cr Mo, W; L = 2,2′-bipyridine, 1,10-phenanthroline, 5-CH3-, 5-Cl-, 5-Br-, 5-NO2-1,10-phenanthroline) have been carried out and reveal that the lowest excited state in every case is charge-transfer (CT) in character, M→ CT in absorption, and in no case do the ligand field (LF) excited states cross below the CT state. Minimum energies of the LF states have been established by the spectroscopic study of cis-bis(pyridine)- and cis-bis(aliphatic amine)-tetracarbonylmetal(0) complexes which all have LF lowest excited states for M = Mo, W. For the M(CO)4L complexes emission is detectable for M = Mo or W and occurs in the range 14.40-15.66 kK with lifetimes of 7.9-13.3 μsec and quantum yields of 0.02–0.09 all in EPA solution at 77 K. For the bis-pyridine and -aliphatic amine complexes emission occurs only from the W complexes and is of the order of 3.0–4.0 kK higher in energy than for the M(CO)4L complexes. Photosubstitution of pyridine is efficient in cis-W(CO)4(py)2 (py = pyridine): Φ436nm = 0.23; Φ405nm = 0.27; and Φ366nm = 0.23. The M(CO)4L complexes have strongly wavelength dependent, but modest, quantum yields for CO substitution and show that the lowest CT state is unreactive. Typical values for CO substitution for M = W and L = 1,10-phenanthroline are: Φ436nm = 1.6 × 10?4; Φ405nm = 1.2 × 10?3; Φ366nm = 9.2 × 10?3; and Φ313nm = 2.2 × 10?2. 相似文献
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Abbott T Akiba Y Beavis D Bloomer MA Bond PD Chasman C Chen Z Chu YY Cole BA Costales JB Crawford HJ Cumming JB Debbe R Engelage J Fung SY Gushue S Hamagaki H Hansen O Hayano RS Hayashi S Homma S Huang HZ Ikeda Y Juricic I Kang J Katcoff S Kaufman S Kimura K Kitamura K Kurita K Ledoux RJ Levine MJ Miake Y Morse RJ Moskowitz B Nagamiya S Olness J Parsons CG Remsberg LP Sakurai H Sarabura M Stankus P Steadman SG Stephans GS Sugitate T Tannenbaum MJ van Dijk JH Videbaek F Vient M Vincent P 《Physical review D: Particles and fields》1992,45(11):3906-3920
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BACKGROUND: Biological silica production has drawn intense attention and several molecules involved in biosilicification have been identified. Cellular mechanisms, however, remain unknown mainly due to the lack of probes required for obtaining information on live specimens. RESULTS: The fluorescence spectra of the compound 2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)methoxy)phenyl)oxazole (PDMPO) are affected by the presence of >3.2 mM silicic acid. Increase in intensity and shift in the fluorescence coincide with the polymerization of Si. The unique PDMPO-silica fluorescence is explored here to visualize Si deposition in living diatoms. The fluorophore is selectively incorporated and co-deposited with Si into the newly synthesized frustules (the outer silica shells) showing an intense green fluorescence. CONCLUSIONS: We suggest that a fluorescence shift is due to an interaction between PDMPO and polymeric silicic acid. PDMPO is an excellent probe for imaging newly deposited silica in living cells and has also a potential for a wide range of applications in various Si-related disciplines, including biology of living organisms as diatoms, sponges, and higher plants, clinical research (e.g. lung fibrosis and cancer, bone development, artificial bone implantation), and chemistry and physics of materials research. 相似文献