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Yajun Zhao Yong Wang Xingping Zhou Zhigang Xue Xianhong Wang Xiaolin Xie Rinaldo Poli 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14449-14456
Switchable polymerization provides the opportunity to regulate polymer sequence and structure in a one‐pot process from mixtures of monomers. Herein we report the use of O2 as an external stimulus to switch the polymerization mechanism from the radical polymerization of vinyl monomers mediated by (Salen)CoIII?R [Salen=N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediamine; R=alkyl] to the ring‐opening copolymerization (ROCOP) of CO2/epoxides. Critical to this process is unprecedented monooxygen insertion into the Co?C bond, as rationalized by DFT calculations, leading to the formation of (Salen)CoIII?O?R as an active species to initiate ROCOP. Diblock poly(vinyl acetate)‐b‐polycarbonate could be obtained by ROCOP of CO2/epoxides with preactivation of (Salen)Co end‐capped poly(vinyl acetate). Furthermore, a poly(vinyl acetate)‐b‐poly(methyl acrylate)‐b‐polycarbonate triblock copolymer was successfully synthesized by a (Salen)cobalt‐mediated sequential polymerization with an O2‐triggered switch in a one‐pot process. 相似文献
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ZnO films doped with different contents of indium were prepared by radio frequency sputtering technique. The structural, optical and emission properties of the films were characterized at room temperature using XRD, XPS, UV-vis-NIR and PL techniques. Results showed that the indium was successfully incorporated into the c-axis preferred orientated ZnO films, and the In-doped ZnO films are of over 80% optical transparency in the visible range. Furthermore, a double peak of blue-violet emission with a constant energy interval (∼0.17 eV) was observed in the PL spectra of the samples with area ratio of indium chips to the Zn target larger than 2.0%. The blue peak comes from the electron transition from the Zni level to the top of the valence band and the violet peak from the InZn donor level to the VZn level, respectively. 相似文献
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A One‐Step Route to CO2‐Based Block Copolymers by Simultaneous ROCOP of CO2/Epoxides and RAFT Polymerization of Vinyl Monomers 下载免费PDF全文
Dr. Yong Wang Yajun Zhao Prof. Dr. Yunsheng Ye Prof. Dr. Haiyan Peng Prof. Dr. Xingping Zhou Prof. Dr. Xiaolin Xie Prof. Dr. Xianhong Wang Prof. Dr. Fosong Wang 《Angewandte Chemie (International ed. in English)》2018,57(14):3593-3597
The one‐step synthesis of well‐defined CO2‐based diblock copolymers was achieved by simultaneous ring‐opening copolymerization (ROCOP) of CO2/epoxides and RAFT polymerization of vinyl monomers using a trithiocarbonate compound bearing a carboxylic group (TTC‐COOH) as the bifunctional chain transfer agent (CTA). The double chain‐transfer effect allows for independent and precise control over the molecular weight of the two blocks and ensures narrow polydispersities of the resultant block copolymers (1.09–1.14). Notably, an unusual axial group exchange reaction between the aluminum porphyrin catalyst and TTC‐COOH impedes the formation of homopolycarbonates. By taking advantage of the RAFT technique, it is able to meet the stringent demand for functionality control to well expand the application scopes of CO2‐based polycarbonates. 相似文献
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We study strictly positive definite functions on the complex Hilbert sphere. A link between strict positive definiteness and
(harmonic) polynomial interpolation on finite‐dimensional spheres is investigated. Sufficient conditions for strict positive
definiteness are presented.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Cen (Math. Numer. Sin. 29(1):39–48, 2007) has defined a weighted group inverse of rectangular matrices. Let A∈C m×n ,W∈C n×m , if X∈C m×n satisfies the system of matrix equations $$(W_{1})\quad AWXWA=A,\quad\quad (W_{2})\quad XWAWX=X,\quad\quad (W_{3})\quad AWX=XWA$$ X is called the weighted group inverse of A with W, and denoted by A W # . In this paper, we will study the algebra perturbation and analytical perturbation of this kind weighted group inverse A W # . Under some conditions, we give a decomposition of B W # ?A W # . As a results, norm estimate of ‖B W # ?A W # ‖ is presented (where B=A+E). An expression of algebra of perturbation is also obtained. In order to compute this weighted group inverse with ease, we give a new representation of this inverse base on Gauss-elimination, then we can calculate this weighted inverse by Gauss-elimination. In the end, we use a numerical example to show our results. 相似文献
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研究考察了在手性(salen)AlCl-叶立德络合物(R,R)-1/2a作为催化剂和异丙醚作为溶剂的条件下,两种不同硅氰化试剂[Me2(CH2Cl)SiCN和Me3SiCN(TMSCN)]在对醛的不对称氰化中的应用情况.一系列不同取代的芳香醛均可分别与这两种试剂发生反应,以高到优秀的产率和对映选择性得到目标产物.脂肪醛的反应产物的对映选择性最高只能达到中等.对比研究发现,Me2(CH2Cl)SiCN在醛的硅氰化反应中显示出了明显高于TMSCN的反应活性,但是产物的对映选择性大体相当. 相似文献
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