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951.
952.
Zhiyuan Qian Luke Galuska William W. McNutt Michael U. Ocheje Youjun He Zhiqiang Cao Song Zhang Jie Xu Kunlun Hong Rene B. Goodman Simon Rondeau‐Gagn Jianguo Mei Xiaodan Gu 《Journal of Polymer Science.Polymer Physics》2019,57(23):1635-1644
Thermomechanical properties of polymers highly depend on their glass transition temperature (T g). Differential scanning calorimetry (DSC) is commonly used to measure T g of polymers. However, many conjugated polymers (CPs), especially donor–acceptor CPs (D–A CPs), do not show a clear glass transition when measured by conventional DSC using simple heat and cool scan. In this work, we discuss the origin of the difficulty for measuring T g in such type of polymers. The changes in specific heat capacity (Δc p) at T g were accurately probed for a series of CPs by DSC. The results showed a significant decrease in Δc p from flexible polymer (0.28 J g?1 K?1 for polystyrene) to rigid CPs (10?3 J g?1 K?1 for a naphthalene diimide‐based D–A CP). When a conjugation breaker unit (flexible unit) is added to the D–A CPs, we observed restoration of the Δc p at T g by a factor of 10, confirming that backbone rigidity reduces the Δc p. Additionally, an increase in the crystalline fraction of the CPs further reduces Δc p. We conclude that the difficulties of determining T g for CPs using DSC are mainly due to rigid backbone and semicrystalline nature. We also demonstrate that physical aging can be used on DSC to help locate and confirm the glass transition for D‐A CPs with weak transition signals. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1635–1644 相似文献
953.
Bardasov I. N. Alekseeva A. U. Dianov N. P. Mikhailov A. A. Ershov O. V. 《Russian Journal of Organic Chemistry》2019,55(11):1731-1734
Russian Journal of Organic Chemistry - Potassium salts of cinnamylidene derivatives of malononitrile trimer were obtained by the reactions of malononitrile trimer with cinnamaldehyde derivatives.... 相似文献
954.
Bünyamin Ak Duygu Elma Nermin Meriç Cezmi Kayan Uğur Işık Murat Aydemir Feyyaz Durap Akın Baysal 《Tetrahedron: Asymmetry》2013,24(20):1257-1264
A new and versatile class of unsymmetrical ferrocenyl-phosphinite ligands possessing a stereogenic center has been prepared from commercially available, inexpensive aminoacids such as, d-, l-phenylglycine and d-, l-phenylalanine, through a concise synthetic procedure. These ligands are not very sensitive to air and moisture, and display good enantioselectivities in the ruthenium-catalyzed asymmetric transfer hydrogenation of acetophenone derivatives, in which up to 91% ee was obtained. A comparison of the catalytic properties of amino alcohols and other analogues based on a ferrocenyl backbone is also discussed briefly. The structures of these ligands and their corresponding complexes have been elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy, and elemental analysis. 相似文献
955.
956.
957.
L. O. Khafizova P. R. Gubaidullin M. G. Shaibakova U. M. Dzhemilev 《Russian Journal of Organic Chemistry》2013,49(6):815-821
A procedure has been developed for the selective synthesis of 1-alkoxy(cycloalkoxy)-1-alkyl-(cycloalkyl)-2-arylcyclopropanes in up to 75% yield by reaction of vinylarenes with aliphatic and cycloalkylacetic acid esters in the presence of Cl n AlEt3 ? n and Cp2ZrCl2 as catalyst. 相似文献
958.
959.
We consider multi-component electrolyte solutions and plasmas in thermal equilibrium and define thermodynamic quantities for number densities which do not necessarily satisfy the condition of charge neutrality. It is shown that these quantities play a role in compressibility theorems for the pair correlation functions and in the generalized Debye shielding length. A fourth moment condition for the pair correlation functions is derived. We discuss to what extent non-uniform systems may be described in terms of local thermodynamics with added coulomb interactions. 相似文献
960.
U. P. Vagin E. S. Kolodochkin A. N. Karkhov N. L. Stal’ 《Russian Journal of Physical Chemistry B, Focus on Physics》2013,7(6):671-673
The paper describes a space monitoring system for powerful impulsive sources designed for detecting storm fronts and lightning activity, predicting powerful magnetic storms, and analyzing the characteristics of faults in the Earth’s curst. It is shown that onboard apparatus can also be used to detect solar and Galactic ionizing-radiation activity, determine the total electron content in the ionosphere, etc. In conclusion, examples of social-economic problems that can be solved using the impulsive-source monitoring system are presented, and perspectives for the further development of this system are discussed. 相似文献