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91.
Romina Marín Antxon Martínez de Ilarduya Sebastián Muñoz‐Guerra 《Journal of polymer science. Part A, Polymer chemistry》2009,47(9):2391-2407
Naturally occurring tartaric acid was used as raw material for the synthesis of novel linear polyurethanes (PURs) bearing two carboxylate side‐groups in the repeating unit. Aliphatic and aromatic PURs were obtained by reaction in solution of alkyl and benzyl tartrates with hexamethylene diisocyanate and 4,4′‐methylene‐bis(phenyl isocyanate), respectively. All the novel PURs were thermally stable and optically active. The aliphatic carboxylate‐containing PURs had Mw in the 40–70 kDa range, with PD between 2.1 and 2.5; all were semicrystalline polymers with melting temperatures between 100 and 150 °C and Tg in the 50–80 °C range. The aromatic PURs were amorphous materials with molecular weights between 18 kDa and 25 kDa and Tg above 130 °C. Hydrogenolysis of the PUR made from hexamethylene diisocyanate and benzyl tartrate yielded PURs containing up to 40% of free carboxylic side‐groups. The tartrate‐derived PURs displayed enhanced sensitivity to hydrolysis compared with their unsubstituted 2,6‐PUR homologs. The PURs bearing free carboxylic groups were unique in being degraded by water upon incubation under physiological conditions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2391–2407, 2009 相似文献
92.
Consider a firm providing home-delivery of small parcels within a short period of time. The paper proposes a method to estimate
the productivity of each driver on any fictitious route using linear regressions. The method separates the trip time in terms
of the time spent: with customers, driving, and all other activities. Our tests show that productivity, measured in terms
of number of customers visited per hour, vary across drivers. Even more, the same driver’s productivity vary for peak and
off-peak demand periods considerably. This methodology should enhance the reliability of the driver scheduling programs, since
it reduces the error and bias of the productivity offered by the assigned set of drivers. It shall also improve the reliability
of the delivery time promised to the customer. 相似文献
93.
94.
B. Esposito F. Felicetti I. Peruzzi M. Piccolo F. Ronga A. Marini B. Bartoli A. Nigro F. Vanoli D. Bisello M. Nigro L. Pescara P. Monacelli L. Paoluzi G.Pi. Ano-Mortari R. Santonico F. Sebasti Ani 《Physics letters. [Part B]》1975,58(4):478-480
A search for narrow resonances in the reaction e+e? → hadrons in the mass regions 1915–2345 MeV and 2970–3090 MeV has been perforned at ADONE, the Frascati storage ring. With 90% confidence level our data exclude the production of narrow resonances with integrated cross section larger than 20% of the integrated cross section for production of the J/Ψ (3100 MeV). 相似文献
95.
Sans résuméA MonsieurHeinrich Behnke, à l'occasion de son 60me anniversaire 相似文献
96.
Comelles J Moreno-Mañas M Pérez E Roglans A Sebastián RM Vallribera A 《The Journal of organic chemistry》2004,69(20):6834-6842
Cu(SbF6)2-AdamBox and copper(II) bis-(5-tert-butylsalicylaldehydate) catalyze the Michael addition in neutral media. Mechanistic studies, based on UV-vis, IR, and electrospray ionization mass spectrometry (ESI-MS), suggest that copper enolates of the beta-dicarbonyl formed in situ are the active nucleophilic species. 相似文献
97.
The ammonium removal efficiency (ARE) and cell viability was investigated in freshly isolated rat hepatocytes exposed to increasing ammonium loads (0.1-2.0 mM). No difference was observed in both ARE and cell viability at the different ammonium concentrations tested. Storage of hepatocytes at 0 degrees C for 72 hours inhibited ammonium removal and urea synthesis. Rewarming of cells at 37 degrees C for 120 min was followed by an ARE fully comparable to freshly isolated hepatocytes. These data indicated that cold preservation of rat hepatocytes for 3 days in UW followed by a rewarming is associated with normal ammonium detoxification efficiency. 相似文献
98.
Leonel Silva Sebastián Tognana Walter Salgueiro 《Journal of Polymer Science.Polymer Physics》2013,51(8):680-686
A differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) study of miscibility in blends of the semicrystalline polyester poly(3-hydroxybutyrate) (PHB) and amorphous monomer epoxy DGEBA (diglycidyl ether of bisphenol A) was performed. Evidence of the miscibility of PHB/DGEBA in the molten state was found from a DSC study of the dependence of glass transition temperature (Tg) as a function of the blend composition and isothermal crystallization, analyzing the melting point (Tm) as a function of blend composition. A negative value of Flory–Huggins interaction parameter χPD was obtained. Furthermore, the lamellar crystallinity in the blend was studied by SAXS as a function of the PHB content. Evidence of the segregation of the amorphous material out of the lamellar structure was obtained. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 相似文献
99.
Bifunctional benzoxazines: Synthesis and polymerization of resorcinol based single isomers
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Hannes Schäfer André Arnebold Johannes Stelten Jordi Marquet Rosa María Sebastián Andreas Hartwig Katharina Koschek 《Journal of polymer science. Part A, Polymer chemistry》2016,54(9):1243-1251
Aside from their outstanding properties such as thermal and chemical stability and excellent mechanical performance, benzoxazines suffer from high polymerization temperatures. Isomeric mixtures of bifunctional benzoxazines based on resorcinol proved already to be highly reactive monomers enabling polymerizations at lower temperatures. This contribution describes the polymerization behavior of single benzoxazine isomers and furthermore the influence of different substituents at the aniline moiety on the curing temperature. Single isomers of bifunctional benzoxazines are now accessible in a straightforward one‐pot synthesis starting from resorcinol and the appropriate N‐phenyl functionalized aniline component. The asymmetric benzoxazine monomers bearing no (R‐a: Tpeak = 179 °C) or electron‐donating substituents in meta position to N (R‐3,5dma: Tpeak = 183 °C) succeed in lowering the polymerization temperature. Additionally, the impact of several initiating systems was studied resulting in a decrease of the polymerization temperature for all studied resorcinol derived benzoxazine isomers (down to 144 °C). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1243–1251 相似文献
100.
M. D. Miranda F. Vaca Chávez T.M.R. Maria M. E. S. Eusébio P.J. Sebastião P. Martín-Ramos 《Molecular Crystals and Liquid Crystals》2016,630(1):87-101
A molecular recognition process has been used to form new mesogenic molecular structures, where intermolecular hydrogen bonding occurs between 4-(octyloxy)benzoic acid (8BAO) and four 4-alkylbenzoic acids (nBAs, n = 2, 5, 6, 7). The synthesis of these complexes has been attained by resorting to mechanochemistry. The resulting materials have been characterized by polarizing optical thermal microscopy, differential scanning calorimetry, vibrational spectroscopy, X-ray powder diffraction, and 1H NMR relaxometry. All the elements of the series show the formation of a mesophase. For one of the complexes, its electro-optical properties have also been assessed, resulting comparable to those of other widely used liquid crystals. 相似文献