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61.
62.
Organic‐acid mediated bulk polymerization of ε‐caprolactam and its copolymerization with ε‐caprolactone 下载免费PDF全文
Ana Sanchez‐Sanchez Andere Basterretxea Daniele Mantione Agustin Etxeberria Cristina Elizetxea Amaia de la Calle Sonia García‐Arrieta Haritz Sardon David Mecerreyes 《Journal of polymer science. Part A, Polymer chemistry》2016,54(15):2394-2402
Polyamides (PA) constitute one of the most important classes of polymeric materials and have gained strong position in different areas, such as textiles, fibers, and construction materials. Whereas most PA are synthesized by step‐growth polycondensation, PA 6 is synthesized by ring opening polymerization (ROP) of ε‐caprolactam (ε‐CLa). The most popular ROP methods involve the use of alkaline metal catalyst difficult to handle at large scale. In this article, we propose the use of organic acids for the ROP of ε‐CLa in bulk at 180 °C (below the polymer's melting point). Among evaluated organic acids, sulfonic acids were found to be the most effective for the polymerization of ε‐CLa , being the Brønsted acid ionic liquid: 1‐(4‐sulfobutyl)?3‐methylimidazolium hydrogen sulfate the most suitable due to its higher thermal stability. End‐group analysis by 1H nuclear magnetic resonance and model reactions provided mechanistic insights and suggested that the catalytic activity of sulfonic acids was a function of not only the acid strength, but of the nucleophilic character of conjugate base as well. Finally, the ability of sulfonic acid to promote the copolymerization of ε‐CLa and ε‐caprolactone is demonstrated. As a result, poly(ε‐caprolactam‐co‐ε‐caprolactone) copolymers with considerably randomness are obtained. This benign route allows the synthesis of poly(ester amide)s with different thermal and mechanical properties. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2394–2402 相似文献
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Inmaculada De La Calle Noelia Cabaleiro Isela Lavilla 《International journal of environmental analytical chemistry》2013,93(14):1401-1411
A simple, fast and reliable method is described for the quantitative extraction of Sb and Co from inorganic environmental matrices containing variable amounts of silicates prior to their determination by electrothermal-atomic absorption spectrometry. The method is based on the ultrasound-assisted extraction of both elements using the mixture 20% v/v HF + 20% v/v HNO3 as extractant. The extraction procedure was carried out in closed Eppendorf vials immersed in a cup-horn sonoreactor for 20?min. Once extraction has been accomplished, the supernatant liquid is separated from the solid phase and subsequently transferred into the autosampler of the instrument. A two-level full factorial design (24) was applied for screening optimisation of the variables influencing the ultrasonic extraction. These variables were: sonication time; amplitude of the ultrasound energy; nitric and hydrofluoric acid concentrations. MLDs were 0.20 and 0.06?µg?·?g?1 for Sb and Co, respectively. Between-batch precision values, expressed as relative standard deviations (n?=?3), were less than 5.5 and 9.6% for Sb and Co, respectively. The method was evaluated using a wide variety of inorganic certified reference materials, such as SRM 2702 (Marine Sediment), SRM 2782 (Industrial Sludge), BCR 176R (Fly Ash), SRM 1633b (Coal Fly Ash) SRM 2710 (Montana Soil) and SRM 2711 (Montana Soil). 相似文献
65.
Sanjurjo Emilio Naya Miguel Ángel Blanco-Claraco José Luis Torres-Moreno José Luis Giménez-Fernández Antonio 《Nonlinear dynamics》2017,88(3):1935-1951
Nonlinear Dynamics - Multibody simulations are already used in many industries to speed up the development of new products. However, improvements in multibody formulations and the continuous... 相似文献
66.
Madeline J. Simpson Horacio Poblete May Griffith Emilio I. Alarcon Juan C. Scaiano 《Photochemistry and photobiology》2013,89(6):1433-1441
The role of recombinant Type‐I human collagen in the free form or forming AgNP@collagen on the photophysical and photochemical behavior of rose Bengal was analyzed. The formation of dye aggregates on the protein surface was experimentally observed and corroborated by docking calculations. The formation of such aggregates is believed to change the main oxidative mechanism from Type‐II (singlet oxygen) to Type‐I (free radical) photosensitization. Remarkably, the presence of AgNP in the form of AgNP@collagen altered the dynamics of dye triplet deactivation, effectively preventing the dye degradation and reducing the extent of protein crosslinked. Both crosslinked rHC and AgNP@collagen were able to support fibroblasts proliferation, but only the material containing silver was resistant to S. epidermidis infection. 相似文献
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Antonio Doménech-Carbó Monserrat Lastras Francisco Rodríguez Emilio Cano Juan Piquero-Cilla Laura Osete-Cortina 《Journal of Solid State Electrochemistry》2014,18(2):399-409
A methodology for monitoring washing procedures applied to stabilize archaeological iron is described. It is based on the combination of voltammetry of microparticles (VMP) with electrochemical impedance spectroscopy (EIS). A semi-empirical approach is used where the impedances at low and high frequencies were related with the fraction areas of passive and corrosion layers generated during the stabilizing treatment, the thickness, and the porosity of the corrosion layer. The variation of such parameters with the time of washing was determined from EIS data for four types of desalination procedures using concentrated NaOH and/or Na2SO3 aqueous solutions on archaeological iron artifacts. After 2 months of treatment, EIS data indicate that an essentially identical “stable” state was attained in all cases, as confirmed by the formation of a passive magnetite layer identified in VMP measurements while the rate of variation of corroded surface and porosity at short washing times varied significantly from one stabilization procedure to another. 相似文献
69.
Probing the CH⋅⋅⋅π Weak Hydrogen Bond in Anesthetic Binding: The Sevoflurane–Benzene Cluster 下载免费PDF全文
Nathan A. Seifert Dr. Daniel P. Zaleski Dr. Cristóbal Pérez Dr. Justin L. Neill Prof. Brooks H. Pate Montserrat Vallejo‐López Prof. Alberto Lesarri Dr. Emilio J. Cocinero Prof. Fernando Castaño Prof. Isabelle Kleiner 《Angewandte Chemie (International ed. in English)》2014,53(12):3210-3213
Cooperativity between weak hydrogen bonds can be revealed in molecular clusters isolated in the gas phase. Here we examine the structure, internal dynamics, and origin of the weak intermolecular forces between sevoflurane and a benzene molecule, using multi‐isotopic broadband rotational spectra. This heterodimer is held together by a primary C? H???π hydrogen bond, assisted by multiple weak C? H???F interactions. The multiple nonbonding forces hinder the internal rotation of benzene around the isopropyl C? H bond in sevoflurane, producing detectable quantum tunneling effects in the rotational spectrum. 相似文献
70.
Dr. Helena Isla Dr. Emilio M. Pérez Prof. Dr. Nazario Martín 《Angewandte Chemie (International ed. in English)》2014,53(22):5629-5633
Supramolecular polymers based on dispersion forces typically show lower molecular weights (MW) than those based on hydrogen bonding or metal–ligand coordination. We present the synthesis and self‐assembling properties of a monomer featuring two complementary units, a C60 derivative and an exTTF‐based macrocycle, that interact mainly through π–π, charge‐transfer, and van der Waals interactions. Thanks to the preorganization in the host part, a remarkable log Ka=5.1±0.5 in CHCl3 at room temperature is determined for the host–guest couple. In accordance with the large binding constant, the monomer self‐assembles in the gas phase, in solution, and in the solid state to form linear supramolecular polymers with a very high degree of polymerization. A MW above 150 kDa has been found experimentally in solution, while in the solid state the monomer forms extraordinarily long, straight, and uniform fibers with lengths reaching several microns. 相似文献