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91.
Ching Hsuan Lin Chun Hung Lin 《Journal of polymer science. Part A, Polymer chemistry》2007,45(14):2897-2912
A new phosphorus‐containing aromatic diamine, 1,4‐bis(4‐aminophenoxy)‐2‐(6‐oxido‐6H‐dibenz[c,e] [1,2]oxaphosphorin‐6‐yl) phenylene ( 3 ) was synthesized by the nucleophilic aromatic substitution of 2‐(6‐oxido‐6H‐dibenz[c,e] [1,2]oxaphosphorin‐6‐yl)‐1,4‐dihydroxy phenylene ( 1 ) with 4‐fluoronitrobenzene, followed by catalytic hydrogenation. Light color, flexible, and creasable polyimides with high molecular weight, high glass transition, high thermal stability, improved organosolubility, and good oxygen plasma resistance were synthesized from the condensation of ( 3 ) with various aromatic dianhydrides in N,N‐dimethylacetamide, followed by thermal imidization. The number‐average molecular weights of polyimides are in the range of 7.0–8.3 × 104 g/mol, and the weight‐average molecular weights are in the range of 12.5–16.5 × 104 g/mol. The Tgs of these polyimides range from 230 to 304 °C by differential scanning calorimetry and from 228 to 305 °C by DMA. These polyimides are tough and flexible, with tensile strength at around 100 MPa. The degradation temperatures (Td 5%) and char yields at 800 °C in nitrogen range from 544 to 597 °C and 59–65 wt %, respectively. Polyimides 5c and 5e , derived from OPDA and 6FDA, respectively, with the cutoff wavelength of 347 and 342 μm, respectively, show very light color. These polyimides also exhibit good oxygen plasma resistance. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2897–2912, 2007 相似文献
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During the last years (2000–2014), many publications concerning the forensic analysis of questioned documents have been published, and new techniques and methodologies are nowadays employed to overcome forensic caseworks. This article reviews a comprehensive collection of the works focused on this issue, including dating studies, the analysis of inks from pens and printers, the analysis of paper, the analysis of other samples related to questioned documents and studies on intersecting lines. These sections highlight the most relevant analytical studies by a wide range of analytical techniques. Separation and spectrometric techniques are critically discussed and compared, emphasizing the advantages and disadvantages of each one. Finally, concluding remarks on the research published are included. 相似文献
94.
Aydan Dag Mehtap Aydin Hakan Durmaz Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2012,50(21):4476-4483
In this work, we used Diels–Alder click reaction for the preparation of various types of aliphatic polycarbonates (PCs). We first prepared a novel anthracene‐functionalized cyclic carbonate monomer, anthracen‐9‐ylmethyl 5‐methyl‐2‐oxo‐1,3‐dioxane‐5‐carboxylate (2), followed by ring‐opening polymerization of this monomer to prepare PC with pendant anthracene groups (PC‐anthracene) using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU)/1‐(3,5‐bis(trifloromethyl)phenyl)‐3‐cyclohexylthiourea (TU) as the catalyst and benzyl alcohol as the initiator in CH2Cl2 at room temperature. Subsequently, the resulting PC‐anthracene (Mn,TDGPC = 6000 g/mol, Mw/Mn = 1.22) was grafted with a linear α‐furan protected‐maleimide terminated‐poly(methyl methacrylate) (PMMA‐MI) (Mn,GPC = 3100 g/mol, Mw/Mn = 1.31), or poly(ethylene glycol) (PEG‐MI) (Mn,GPC = 550 g/mol, Mw/Mn = 1.09), or a mixture of PMMA‐MI and PEG‐MI to yield well‐defined PC graft or hetero graft copolymers, PC‐g‐PMMA (Mn,TDGPC = 59000 g/mol, Mw/Mn = 1.22) or PC‐g‐PEG, or PC‐g‐(PMMA)‐co‐PC‐g‐(PEG) (Mn,TDGPC = 39900 g/mol, Mw/Mn = 1.16), respectively, using Diels–Alder click reaction in toluene at 110°C. The Diels–Alder grafting efficiencies were found to be over 97% using UV spectroscopy. Moreover, the structural analyses and the molecular weights of resulting graft copolymers were determined via 1H NMR and triple detection GPC (TD‐GPC), respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
95.
Synthesis of poly(1‐chloro‐2‐arylacetylene)s with high cis‐content and examination of their absorption/emission properties 下载免费PDF全文
Jesus Rodriguez Castanon Natsuhiro Sano Masashi Shiotsuki Fumio Sanda 《Journal of polymer science. Part A, Polymer chemistry》2017,55(3):382-388
A series of 1‐chloro‐2‐arylacetylenes [Cl‐C?C‐Ar, Ar = C6H5 ( 1 ), C6H4‐p‐i Pr ( 2 ), C6H4‐p‐Oi Pr ( 3 ), C6H4‐p‐NHC(O)Ot Bu ( 4 ), and C6H4‐o‐i Pr ( 5 )] were polymerized using (tBu3P)PdMeCl/silver trifluoromethanesulfonate (AgOTf) and MoCl5/SnBu4 catalysts. The corresponding polymers [poly( 1 )–poly( 5 )] with weight‐average molecular weights of 6,500–690,000 were obtained in 10–91% yields. THF‐insoluble parts, presumably high‐molecular weight polymers, were formed together with THF‐soluble polymers by the Pd‐catalyzed polymerization. The Pd catalyst polymerized nonpolar monomers 1 and 2 to give the polymers in yields lower than the Mo catalyst, while the Pd catalyst polymerized polar monomers 3 and 4 to give the corresponding polymers in higher yields. The 1H NMR and UV–vis absorption spectra of the polymers indicated that the cis‐contents of the Pd‐based polymers were higher than those of the Mo‐based polymers, and the conjugation length of the Pd‐based polymers was shorter than that of the Mo‐based polymers. Pd‐based poly( 5 ) emitted fluorescence most strongly among poly( 1 )–poly( 5 ). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 382–388 相似文献
96.
Chun Du Weiwei Li Cuihong Li Zhishan Bo 《Journal of polymer science. Part A, Polymer chemistry》2013,51(2):383-393
Four ethynylene‐containing donor‐acceptor alternating conjugated polymers P1 – P4 with 2,5‐bis(dodecyloxy) substituted phenylene or carbazole as the donor unit and benzothiadiazole (BTZ) as the acceptor unit were synthesized and used as donor polymers in bulk heterojunction polymer solar cells. The optical, electrochemical, and photovoltaic properties of these four polymers with the ethylene unit located at different positions of the polymer chains were systematically investigated. Our results demonstrated that absorption spectra and the HOMO and LUMO energy levels of polymers could be tuned by varying the position of the ethynylene unit in the polymer chains. Photovoltaic devices based on polymer/PC71BM blend films spin coated from chloroform and dichlorobenzene solutions were investigated. For all four polymers, open circuit voltages (Voc) higher than 0.8 V were obtained. P4 , with ethynylene unit between BTZ and thiophene, shows the best performance among these four polymers, with a Voc of 0.94 V, a Jsc of 4.2 mA/cm2, an FF of 0.40, and a PCE of 1.6%. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
97.
Second‐order rate constants were gathered for solution Diels–Alder reactions of substituted and unsubstituted acenes, with the intention of ascertaining ideal diene–dienophile combinations. Particular focus was placed on the larger ring systems namely tetracene, pentacene, and rubrene. The rate constants between the acenes ranged roughly six orders of magnitude, from the slowest reacting diene, rubrene, to the fastest diene, pentacene. The utilized dienophiles covered a large range of reactivity from 2,3‐dichloromaleic anhydride to tetracyanoethylene. To aid in the interpretation of acene reactivity, constants were compared to the extensive body of Diels–Alder literature with well‐studied dienes such as anthracene and trans‐1‐methoxy‐1,3‐butadiene serving as points of reference. Complex reaction kinetics for the addition of MeTAD and rubrene was found: initial fast consumption generated an intermediate, followed by dramatically slower product formation. The kinetic data creates a foundation for the analysis of prior and future reactions between organic semiconductor acene materials with volatized dienophiles, a surface functionalization technique for enhancing these electronic materials. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Studies of heavy lanthanide chlorides may provide important information on the degree of Ln3+–ligand bond covalency. Monocrystals of LnCl3·6H2O, where Ln = Dy, Ho and Er, were grown and spectroscopic investigations were performed at room temperature and at low temperatures down to 4.2 K in order to understand the nature of the Ln3+–L bonds. The intensities of the electronic lines and the Judd–Ofelt parameters were calculated and compared with those obtained for chlorides of light lanthanides (i.e. Ce(III), Pr(III) and Nd(III)). Room temperature Raman and IR studies of the compounds under investigation were also performed. The relationship between hypersensitivity and covalency is discussed. The change of vibronic coupling strength along the lanthanide ion series does not modify monotonically. The ion-pair interactions are especially visible for the 5I8 → 5F2 and 5I8 → 5F3 transitions in the HoCl3·6H2O low temperature spectra. 相似文献
100.
Agnieszka Iwan Patrice Rannou 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(1):174-179
The UV–vis absorption properties of undoped and doped 1,4-phenylenemethylidynenitrilo-1,4-phenylenenitrilomethylidyne (PAZ) in various temperatures are reported. It is demonstrated that the absorption spectra can be modified not only by changing the temperature from 193 K to 413 K, but also via acid–base doping involving the protonation of nitrogen atom in imine group. The use of special protonating agent, i.e. 1,2-(di-2-ethylhexyl)ester of 4-sulfophthalic acid (PSA) lead to the modification of the absorption spectrum of the PAZ. The imine band in UV–vis spectrum of the doped with the PSA polyazomethine is 85 nm red shifts in comparison with unprotonated one. The thermochromism of PAZ included the conformational changes in the conjugating backbone structure of the undoped and doped polyazomethine. 相似文献