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991.
Irina Brailovsky Peter Gordon Gregory Sivashinsky 《Combustion Theory and Modelling》2019,23(4):573-591
The paper is concerned with the experimentally known phenomenon that the detonation velocity of a tubular charge may markedly exceed that of a homogeneous charge of the same explosive. It is shown that the effect may be successfully reproduced using a simple quasi-one-dimensional two-layer model assuming the gas–solid system to be isothermal and the volumetric fraction of the solid phase to be small. In view of a considerable drop of the burned gas pressure/density, compared to the Chapman–Jouguet case, fast detonation may be perceived as a variety of weak (undercompressed) detonation. 相似文献
992.
Prof. Dr. Ryo Sekiya Prof. Dr. Takeharu Haino 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):187-199
Nanographenes (NGs) have recently emerged as new carbon materials. Their nanoscale size results in a size-dependent quantum confinement effect, opening the band gap by a few eV. This energy gap allows NGs to be applied as optical materials. This property has attracted researchers across multiple scientific fields. The photophysical properties of NGs can be manipulated by introducing organic groups onto their basal planes and/or into their edges. In addition, the integration of organic functional groups into NGs results in NG-based hybrid materials. These features make the post-synthetic modification of NGs an active research area. As obtainable information on chemically functionalized NGs is limited owing to their nonstoichiometry and structural uncertainty, their structural characterization requires a combination of multiple spectroscopic methods. Therefore, information on the characterization procedures of recently published chemically functionalized NGs is of value for advancing the field of NG-based hybrid materials. The present review focuses on the structural characterization of chemically functionalized NGs. It is hoped that this review will help to advance this field. 相似文献
993.
Daniel J. G. Johnson Ian D. Jenkins Cohan Huxley Mark J. Coster Kah Yean Lum Jonathan M. White Vicky M. Avery Rohan A. Davis 《Molecules (Basel, Switzerland)》2021,26(9)
A radical approach to late-stage functionalization using photoredox and Diversinate™ chemistry on the Open Source Malaria (OSM) triazolopyrazine scaffold (Series 4) resulted in the synthesis of 12 new analogues, which were characterized by NMR, UV, and MS data analysis. The structures of four triazolopyrazines were confirmed by X-ray crystal structure analysis. Several minor and unexpected side products were generated during these studies, including two resulting from a possible disproportionation reaction. All compounds were tested for their ability to inhibit the growth of the malaria parasite Plasmodium falciparum (3D7 and Dd2 strains) and for cytotoxicity against a human embryonic kidney (HEK293) cell line. Moderate antimalarial activity was observed for some of the compounds, with IC50 values ranging from 0.3 to >20 µM; none of the compounds displayed any toxicity against HEK293 at 80 µM. 相似文献
994.
Shanta Pokhrel 《高分子科学杂志,A辑:纯化学与应用化学》2019,56(5):450-475
The deacetylated derivative of chitin i.e. chitosan is an advantageous and interesting bioactive polymer. Despite its biodegradability, it consists of many reactive primary and secondary hydroxyl (–OH) and amino (–NH2) functional groups which allow the possibilities of chemical modifications. The several chemical modifications such as alkylation, acylation, quaternization, phthaloylation, sulfation, thiolation, carboxymethylation, graft copolymerization etc. carried out. The chemical modification results various types of derivatives with modified properties for specific applications in varied area mainly of pharmaceutical, biomedical, biotechnological, cosmetic, agricultural, food and non-food industries as well as in water treatment, paper, and textile industry. The ability of chitosan to undergo versatile modifications and applications presents a great opportunity to scientific community and to industry. 相似文献
995.
Kosuke Makiguchi Seiya Kikuchi Kazuma Yanai Yoshitaka Ogasawara Shin‐ichiro Sato Toshifumi Satoh Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2014,52(7):1047-1054
The ring‐opening polymerizations (ROPs) of ε‐caprolactone (ε‐CL) and L ‐lactide (LLA) have been studied using the organocatalysts of diphenyl phosphate (DPP) and 4‐dimethylaminopyridine (DMAP). The “dual activation” property of DPP and the “bifunctional activation” property of DPP/DMAP were confirmed by the NMR measurement for ε‐CL and its chain‐end model of poly(ε‐caprolactone) and for LLA and its chain‐end model of poly(L ‐lactide) (PLLA), respectively. The molar ratio of DPP/DMAP was optimized as 1/2 for the ROP of LLA leading to the well‐defined PLLA, such as the molecular weight determined from 1H NMR measurement of 19,200 g mol?1 and the narrow polydispersity of 1.10. Additionally, functional initiators were utilized for producing the end‐functionalized PLLAs. The DPP‐catalyzed ROPs of ε‐CL and its analogue cyclic monomers and then the DPP/DMAP‐catalyzed ROP of LLA produced block copolymers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1047–1054 相似文献
996.
Miao Hong San‐Rong Liu Bai‐Xiang Li Yue‐Sheng Li 《Journal of polymer science. Part A, Polymer chemistry》2012,50(12):2499-2506
A series of functional polyethylenes have been simply and efficiently synthesized via the combination of regioselective ethylene/5‐vinyl‐2‐norbornene (VNB) copolymerization using [PhNC(CF3)CHCO(Ph)]2TiCl2 catalyst and following ultraviolet light initiated thiol‐ene click reaction. On treatment of ethylene/VNB copolymer with different thiols including mercaptoethanol, 1‐thioglycerol, methyl mercaptoacetate, methyl mercaptopropionate, 2‐mercaptoethylamine, mercaptoacetic acid, and mercaptopropanoic acid, various polar groups have been successfully introduced into the polyethylene. Except 2‐mercaptoethylamine, the functionalizations are quite efficient with the degree of functionalization higher than 94%, which is independent of thiol structure and double bond content. The content of polar group in functional polyethylene can be tuned in a wide range of 0–30 mol %. Gel permeation chromatography profiles indicate all functional polyethylenes that have very high molecular weights (160–336 kg/mol) with homogeneous formation. Besides, systematic investigation of the influence of vinyl type and thiol structure on reactivity has been also carried out. By treatment of mercaptoethanol with different copolymers (ethylene/VNB, ethylene/5‐ethylidene‐2‐norbornene, and ethylene/dicyclopentadiene copolymer), the order of vinyl reactivity can be summarized as terminal > internal > cyclic double bond. For different thiols, the reactivity has the sequence of SHCH2COOH > SHCH2COOCH3 > SHCH2CH2COOH > SHCH2CH2COOCH3 > SHCH2CH(OH)CH2OH > SHCH2CH2OH > SHCH2CH2NH2, which is depended on the solubility and the electron‐withdrawing inductive effect of polar group. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
997.
Marta Palacios‐Cuesta Marta Liras Christine Labrugère Juan Rodríguez‐Hernández Olga García 《Journal of polymer science. Part A, Polymer chemistry》2012,50(23):4902-4910
A new procedure focused on the design and preparation of structured and functional polymer surfaces by combination of two approaches acting simultaneously is developed. The elaboration of micrometer size patterned surfaces by UV‐light lithography is reported where, in addition, the surface chemical composition can be controlled by surface segregation of a fluorinated copolymer incorporated in the photopolymerizable mixture. As evidenced by contact angle and XPS measurements, the surface composition can be modified depending on such factors as with the environmental conditions or the concentration of copolymer in the blend. Moreover, the functionality of the copolymer is enhanced by the surface pattern created. As a consequence, the wettability of the films can be modified depending on the pattern and composition of the blend. By using this methodology, functional adaptive sensitive surfaces with a well‐defined topography will be obtained in one single step and without the use of tedious and time‐consuming multistep procedures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
998.
Young‐Hoon Seo Woo‐Hyung Lee Jong‐Hyeok Park Cheolbeom Bae Yongtaek Hong Jong‐Wook Park In‐Nam Kang 《Journal of polymer science. Part A, Polymer chemistry》2012,50(4):649-658
A series of new phenothiazine‐based donor–acceptor copolymers, P1 and P2, were synthesized via a Suzuki coupling reaction. The weight‐averaged molecular weights (Mw) of P1 and P2 were found to be 16,700 and 16,100, with polydispersity indices of 1.74 and 1.39, respectively. The UV–visible absorption spectra of the polymer thin films contained three strong absorption bands in the ranges 318–320 nm, 430–436 nm, and 527–568 nm. The absorption peaks at 320 and 430 nm originated mainly from the phenothiazine‐based monomer units, and the longer wavelength absorption band at 527–568 nm was attributed to the increased effective conjugation length of the polymer backbones. Solution‐processed field‐effect transistors fabricated with these polymers exhibited p‐type organic thin film transistor characteristics. The field‐effect mobilities of P1 and P2 were measured to be 1.0 × 10?4 and 7.5 × 10?5 cm2 V?1 s?1, respectively, with on/off ratios in the order of 104 for all polymers. A photovoltaic device in which a P2/PC71BM (1/3) blend film was used as the active layer exhibited an open‐circuit voltage (VOC) of 0.70 V, a short‐circuit current (JSC) of 6.79 mA cm(2, a fill factor of 0.39, and a power conversion efficiency of 1.86% under AM 1.5 G (100 mW cm?2) illumination. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
999.
《Electroanalysis》2017,29(4):1056-1061
Functionalized high purity carbon nanotubes (CNTs) with various amounts of oxygen containing surface groups were investigated towards the relevant redox reactions of the all‐vanadium redox flow battery. The quinone/hydroquinone redox peaks between 0.0 and 0.7 V vs. Ag|AgCl|KClsat. were used to quantifying the degree of functionalization and correlated to XPS results. Cyclic voltammetry in vanadyl sulfate‐containing 3 M H2SO4 as a common supporting electrolyte showed no influence of the amount of surface groups on the V(IV)/V(V) redox system. In contrast, the reactions occurring at the negative electrode (V(II)/V(III) and V(III)/V(IV)) are strongly affected by oxygen surface groups. However, under modified experimental conditions, SECM experiments detecting the consumption of VO2+ molecules by CNT thin films in pH=2 solution show improved onset potentials with increased surface oxygen content up to ∼ 3 at%. Further increase in surface oxygen up to 8 at% led to minor improvement. These dissimilar results under different experimental conditions are rationalized by suggesting that oxygen functional groups do not form the active site for the V(IV)/V(V) reaction but wetting of the catalyst layer is of high importance. 相似文献
1000.