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71.
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Francesco Babudri Antonio Cardone Gianluca M. Farinola Raffaele Tommasi 《Journal of organometallic chemistry》2008,693(15):2631-2636
Poly(2′,5′-dioctyloxy-4,4′,4″-terphenylenevinylene) with (E) configuration of the vinylene double bonds was prepared by Suzuki-Miyaura polymerization of (E)-4,4′-dibromostilbene and 2,5-dioctyloxy-1,4-benzenediboronic acid. Attempts to extend this simple procedure to the synthesis of the polymer with (Z) configuration, starting from (Z)-4,4′-dibromostilbene, were unsuccessful. However, the use of (Z)-4,4′-diiodostilbene and a careful choice of Pd catalyst and experimental conditions, lead to a material with a >95/<5 (Z)/(E) ratio of vinylene units. The investigation of optical properties of both the (E) and (Z) polymers evidenced that (Z) linkages act as defects which reduce the effective conjugation length in the polymer backbone. 相似文献
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In the inflationary scenario of loop quantum cosmology in the presence of inverse-volume corrections, we give analytic formulas for the power spectra of scalar and tensor perturbations convenient to compare with observations. Since inverse-volume corrections can provide strong contributions to the running spectral indices, inclusion of terms higher than the second-order runnings in the power spectra is crucially important. Using the recent data of cosmic microwave background and other cosmological experiments, we place bounds on the quantum corrections. 相似文献
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Filippo Samperi Salvatore Battiato Concetto Puglisi Vincenzo Asarisi Antonino Recca Gianluca Cicala Raniero Mendichi 《Journal of polymer science. Part A, Polymer chemistry》2010,48(14):3010-3023
The present article deals with the synthesis and characterization of some sulfonated copolyethersulfones. The synthetic approach differs from the post sulfonation approach traditionally reported in the literature. The synthetic procedure is based on the use of sulfonated monomers which are then reacted with previously synthesized telechelic hydoxy‐ended poly (ether sulpnone)s. Combining the MALDI‐TOF MS and 1H NMR analyses, with SEC‐Viscometry and TGA measurements, we demonstrate a powerful tool for characterizing the chemical composition, end chains, degree of sulfonation (DS) and molecular mass distribution (MMD) of disulfonated poly(arylene ether‐sulfone) copolymers. The characterization techniques allowed to determine the exact nature of the copolymers synthesized and to reveal some interesting features about the reaction. DMA data show that the glass transition temperature of sulfonated copolymers with similar DS increase as raise their MMD. Copolymers with a DS of 10–11 mol % reach a Tg of 244–246 °C. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3010–3023, 2010 相似文献
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Conformationally restricted analogues of β-methylaspartic acid were easily prepared starting from chiral N-protected trans-3-amino-4-methoxycarbonyl pyrrolidin-2-ones. The key step of the synthesis was the methylation reaction at C-4, proceeding with high diastereoselection syn to the protected amino group lying at C-3 of the pyrrolidin-2-one ring. 相似文献
79.
Mohammadreza Shariatgorji Zdenek Spacil Gianluca Maddalo Lourdes B. Cardenas Leopold L. Ilag 《Rapid communications in mass spectrometry : RCM》2009,23(23):3655-3660
Quaternary protoberberine alkaloids belong to a pharmaceutically important class of isoquinoline alkaloids associated with bactericidal, fungicidal, insecticidal and antiviral activities. As traditional medicine gains wider acceptance, quick and robust analytical methods for the screening and analysis of plants containing these compounds attract considerable interest. Thin‐layer chromatography (TLC) combined with matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) is a powerful technique but suffers from dilution of the TLC bands resulting in decreased sensitivity and masking of signals in the low‐mass region both due to addition of matrix. This study integrates for the first time conventional silica gel TLC and laser desorption ionization mass spectrometry (LDI‐MS) thus eliminating the need for any external matrix. Successful separation of berberine (Rf = 0.56) and palmatine (Rf = 0.46) from Berberis barandana including their identification by MS are demonstrated. Furthermore, a robust electrospray ionization (ESI)‐MS method utilizing residual sample from TLC for quantification of berberine applying selected reaction monitoring and standard addition method is presented. The amount of berberine in the plant root prepared for the study was determined to be 0.70% (w/w). Copyright © 2009 John Wiley & Sons, Ltd. 相似文献