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Supramolecular Copolymerization as a Strategy to Control the Stability of Self‐Assembled Nanofibers 下载免费PDF全文
Bala N. S. Thota Xianwen Lou Davide Bochicchio Tim F. E. Paffen René P. M. Lafleur Joost L. J. van Dongen Svenja Ehrmann Rainer Haag Giovanni M. Pavan Anja R. A. Palmans E. W. Meijer 《Angewandte Chemie (International ed. in English)》2018,57(23):6843-6847
A major challenge in supramolecular polymerization is controlling the stability of the polymers formed, that is, controlling the rate of monomer exchange in the equilibrium between monomer and polymer. The exchange dynamics of supramolecular polymers based on benzene‐1,3,5‐tricarboxamide (BTA) can be regulated by copolymerizing molecules with dendronized (dBTA) and linear (nBTA) ethylene glycol‐based water‐soluble side chains. Whereas nBTAs form long nanofibers in water, dBTAs do not polymerize, forming instead small spherical aggregates. The copolymerization of the two BTAs results in long nanofibers. The exchange dynamics of both the BTA monomers in the copolymer are significantly slowed down in the mixed systems, leading to a more stable copolymer, while the morphology and spectroscopic signature of the copolymers are identical to that of nBTA homopolymer. This copolymerization is the supramolecular counterpart of styrene/ maleic anhydride copolymerization. 相似文献
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On Silylated Oxonium and Sulfonium Ions and Their Interaction with Weakly Coordinating Borate Anions
Kevin Bläsing Dr. Rene Labbow Dr. Dirk Michalik Dr. Fabian Reiß Prof. Dr. Axel Schulz Dr. Alexander Villinger Svenja Walker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(7):1640-1652
Attempts have been made to prepare salts with the labile tris(trimethylsilyl)chalconium ions, [(Me3Si)3E]+ (E=O, S), by reacting [Me3Si-H-SiMe3][B(C6F5)4] and Me3Si[CB] (CB−=carborate=[CHB11H5Cl6]−, [CHB11Cl11]−) with Me3Si-E-SiMe3. In the reaction of Me3Si-O-SiMe3 with [Me3Si-H-SiMe3][B(C6F5)4], a ligand exchange was observed in the [Me3Si-H-SiMe3]+ cation leading to the surprising formation of the persilylated [(Me3Si)2(Me2(H)Si)O]+ oxonium ion in a formal [Me2(H)Si]+ instead of the desired [Me3Si]+ transfer reaction. In contrast, the expected homoleptic persilylated [(Me3Si)3S]+ ion was formed and isolated as [B(C6F5)4]− and [CB]− salt, when Me3Si-S-SiMe3 was treated with either [Me3Si-H-SiMe3][B(C6F5)4] or Me3Si[CB]. However, the addition of Me3Si[CB] to Me3Si-O-SiMe3 unexpectedly led to the release of Me4Si with simultaneous formation of a cyclic dioxonium dication of the type [Me3Si-μO-SiMe2]2[CB]2 in an anion-mediated reaction. DFT studies on structure, bonding and thermodynamics of the [(Me3Si)3E]+ and [(Me3Si)2(Me2(H)Si)E]+ ion formation are presented as well as mechanistic investigations on the template-driven transformation of the [(Me3Si)3E]+ ion into a cyclic dichalconium dication [Me3Si-μE-SiMe2]22+. 相似文献
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Victor Brosius Svenja Weigold Nikolai Hippchen Dr. Frank Rominger Dr. Jan Freudenberg Prof. Dr. Uwe H. F. Bunz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(39):10001-10005
The syntheses, properties and application of the air-stable electron acceptors, diindenopyrazines 4 a – g are reported demonstrating the introduction of functional aryl groups in the 6- and 12-positions. The targets are accessible on the hundred milligram to gram scale. The structure of the aryl groups in 4 a – g modulates their solubility, redox potentials and optical properties. The introduction of electron-poor aryl groups to the electron-poor diindenopyrazine backbone reduces the electron affinity to −4 eV, making the compounds attractive as n-semiconductors. A simple organic field-effect transistor of 4 e –without optimization– shows electron transport with a mobility of up to 0.037 cm2 V−1 s−1. 相似文献
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Berger Thomas Drücker Svenja Lanza Lukas Reis Timo Seifried Robert 《Nonlinear dynamics》2021,104(4):3671-3699
Nonlinear Dynamics - We consider tracking control for multibody systems which are modeled using holonomic and non-holonomic constraints. Furthermore, the systems may be underactuated and contain... 相似文献
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Wang YJ Eardley M Knappe S Moreland J Hollberg L Kitching J 《Physical review letters》2006,97(22):227602
We demonstrate a direct resonant interaction between the mechanical motion of a mesoscopic resonator and the spin degrees of freedom of a sample of neutral atoms in the gas phase. This coupling, mediated by a magnetic particle attached to the tip of the miniature mechanical resonator, excites a coherent precession of the atomic spins about a static magnetic field. The novel coupled atom-resonator system may enable development of low-power, high-performance sensors, and enhance research efforts connected with the manipulation of cold atoms, quantum control, and high-resolution microscopy. 相似文献
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Edna Bode Antje K. Heinrich Merle Hirschmann Desalegne Abebew Yan‐Ni Shi Tien Duy Vo Frank Wesche Yi‐Ming Shi Peter Grün Svenja Simonyi Nadine Keller Yvonne Engel Sebastian Wenski Reuel Bennet Sophie Beyer Iris Bischoff Anthony Buaya Sophie Brandt Ibrahim Cakmak Harun imen Simone Eckstein Denia Frank Robert Fürst Martin Gand Gerd Geisslinger Selcuk Hazir Marina Henke Ralf Heermann Virginie Lecaudey Wilhelm Schfer Susanne Schiffmann Anja Schüffler Rebecca Schwenk Marisa Skaljac Eckhard Thines Marco Thines Thomas Ulshfer Andreas Vilcinskas Thomas A. Wichelhaus Helge B. Bode 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(52):19133-19139
Natural products (NPs) from microorganisms have been important sources for discovering new therapeutic and chemical entities. While their corresponding biosynthetic gene clusters (BGCs) can be easily identified by gene‐sequence‐similarity‐based bioinformatics strategies, the actual access to these NPs for structure elucidation and bioactivity testing remains difficult. Deletion of the gene encoding the RNA chaperone, Hfq, results in strains losing the production of most NPs. By exchanging the native promoter of a desired BGC against an inducible promoter in Δhfq mutants, almost exclusive production of the corresponding NP from the targeted BGC in Photorhabdus, Xenorhabdus and Pseudomonas was observed including the production of several new NPs derived from previously uncharacterized non‐ribosomal peptide synthetases (NRPS). This easyPACId approach (easy Promoter Activated Compound Identification) facilitates NP identification due to low interference from other NPs. Moreover, it allows direct bioactivity testing of supernatants containing secreted NPs, without laborious purification. 相似文献
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Stefan Helber Katja Schimmelpfeng Raik Stolletz Svenja Lagershausen 《Annals of Operations Research》2011,182(1):193-211
This paper presents a linear programming approach to analyze and optimize flow lines with limited buffer capacities and stochastic
processing times. The basic idea is to solve a huge but simple linear program that models an entire simulation run of a multi-stage
production process in discrete time, to determine a production rate estimate. As our methodology is purely numerical, it offers
the full modeling flexibility of stochastic simulation with respect to the probability distribution of processing times. However,
unlike discrete-event simulation models, it also offers the optimization power of linear programming and hence allows us to
solve buffer allocation problems. We show under which conditions our method works well by comparing its results to exact values
for two-machine models and approximate simulation results for longer lines. 相似文献