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CRYSTALLIZATION KINETICS OF HOMOGENEOUS AND HETEROGENEOUS LLDPE

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chinese Journal of polymer science 2002年第4期20卷 339-345页

作者： Hong-xiang Teng Wen-hong Tang Yi Shi xi-gao jin state key laboratory of polymer physics and chemistry center for molecular science, institute of chemistry chinese academy of sciences beijing 100080 china Department of chemistry Jilin University Changchun 130023, china center for molecular science Institute of Chemistry Chinese Academy of Sciences State Key Laboratory of Polymer Physics and Chemistry 北京 100080 Department of chemistry Jilin University Changchun 130023

Based on thermal analysis, the isothermal and nonisothemal crystallization kinetics of Ziegler-Natta catalyzed linear low density polyethylene (Z-N LLDPE) and metallocene catalyzed LLDPE (m-LLDPE) were studied. Treating the results with the Avrami equation and the Ozawa equation, the crystallization constant Igk and the Avrami exponent n were obtained. Some other crystallization parameters were also discussed. According to the different characteristics of the chain structures of Z-N LLDPE and metallocene LLDPE, their crystallization behaviors were analyzed. It is indicated that the homogeneity and heterogeneity of the two polymers act in different way during the crystallization process of polymers, including the nucleation and the growth of crystals under various conditions.

关键词： crystallization kinetics homogeneity heterogeneity LLDPE

Interfacial behaviors of PMMA-PEO block copolymers at the air/water interface

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science china chemistry 2005年第6期48卷 567-573页

作者： CHENG Caixia1, JIAO Tifeng2, TANG Rupei1, LIU Minghua2 & xi Fu1 1. state key laboratory of polymer physics and chemistry, Joint laboratory of polymer science and Materials, institute of chemistry, chinese academy of sciences, beijing 100080, china 2. CAS key laboratory of Colloid and Interface science, institute of chemistry, chinese academy of sciences, beijing 100080, china state key laboratory of polymer physics and chemistry Joint Laboratory of Polymer Science and Materials Institute of Chemistry Chinese Academy of Sciences Beijing China CAS key laboratory of Colloid and Interface science Institute of Chemistry Chinese Academy of Sciences Beijing China

Diblock copolymer of PMMA291-b-PEO114 and triblock copolymer of PMMA120-b- PEO227-b-PMMA120 were synthesized and their interfacial properties at the air-water interface were investigated, where both blocks of polyethylene oxide (PEO) and poly(methyl methacrylate) (PMMA) are surface active but the former is soluble in water while the latter is not. Both the block copolymers could form monolayers with two obvious transition regions. The first transition point is around 10 mN/m, which could be assigned to the pancake-brush change of the PEO chains. The other is around 18 mN/m, which could be ascribed to the condensed packing of PMMA. The surface morphological changes during the compression of the Langmuir monolayers are inves-tigated by using the AFM and SEM methods for the films deposited at different surface pressure or molecular areas. At a lower surface pressure, a typical morphology of PEO-con- taining lipopolymers is observed. Upon compression, sphere-dominant morphologies were observed. While the diblock copolymer is easy to folding, the triblock copolymer is in favor of formation of circular domains through vesiculation.

关键词： PMMA-PEO, block copolymers, monolayer, Langmuir-Blodgett films, AFM.

MORPHOLOGICAL STUDY ON THE ORIENTED CHITOSAN FILM OBTAINED FROM PRE-SHEARED LIQUID CRYSTALLINE SOLUTION IN DICHLOROACETIC ACID

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chinese Journal of polymer science 2001年第4期19卷 385-390页

作者： Zhong-ming Hu Li-heng Wu Da-cheng Wu Shou-xi Chen state key laboratory of polymer physics and chemistry, center for molecular science, institute of chemistry chinese academy of sciences, beijing 100080, china china Textile academy beijing 100025, china Textile College, Sichuan University Chengdu 610065, china 中科院化学所高分子物理与化学国家重点实验室北京中国纺织研究院北京四川大学四川成都

The oriented chitosan films obtained from pre-sheared liquid crystalline chitosan/dichloroacetic acid (DCA) solutions were studied by means of polarized optical microscopy (POM), scanning electron microscopy (SEM), infra-red dichroism technique and wide angle X-ray diffraction (WAXD). The sheer induced band texture in the film was found to correspond to the sinusoidal fibrillar microstructure along the shearing direction on the basis of POM and SEM observations. The sinusoidal fibril was found to be lying within the film plane. The model of chitosan molecular orientation in the pre-sheared film with band texture can be established assuming that the main chain orients in the shearing direction and the side group is perpendicular to the shearing direction. The WAXD azimuthal scanning at 2 theta = 20 degrees indicates that the (002) plane orients perpendicular to the shearing direction.

关键词： chitosan morphology orientation shear induced band texture liquid crystalline solution

Highly stereospecific polymerization of isoprene with homogeneous binary Ziegler-Natta catalysts based on NCN-pincer neodymium precursor

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science china chemistry 2010年第8期53卷 1641-1645页

作者： LIU DongTao1,2,CUI DongMei1 & gao Wei3 1state key laboratory of polymer physics and chemistry Changchun institute of Applied chemistry,chinese academy of sciences,Changchun 130022,china 2Graduate University of chinese academy of sciences,beijing 100039,china 3School of chemistry,Jilin University,Changchun 130012,china state key laboratory of polymer physics and chemistry Changchun institute of Applied chemistry Chinese Academy of Sciences Changchun China Graduate University of chinese academy of sciences Beijing China School of chemistry Jilin University Changchun China

The aryldiimine NCN-pincer stabilized neodymium dichloride combined with aluminum alkyls established a new type of homogeneous binary neutral Ziegler-Natta catalyst *** system exhibited high activity and high cis-1,4 selectivity for the polymerization of isoprene (Tp=20 °C,98.2%;Tp=-20 °C,> 99%).Such catalytic performances remained under a broad range of polymerization temperatures and monomer-to-neodymium ratios (from 500 to 8000),reaching high number-average molecular weight (Mn=1582 kg/mol) and relatively narrow molecular weight distribution (PDI=1.68),which was,however,influenced by the amount and bulkiness of aluminum *** investigation of the polymerization was performed,which showed the number-average molecular weight of the resultant polyisoprene had an almost linear correlation with the conversion,suggesting,in some degree,the polymerization with this catalytic system was controllable.

关键词： neodymium cis-1 4 selectivity NCN-pincer complex polyisoprene

Solid state NMR and Fluorescence Studies of Conjugated polymer Nanocomposties

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chinese Chemical Letters 2005年第11期16卷 1519-1522页

作者： Chao Jun jinG Liu Sheng CHEN Yi SHI xi gao jin state key laboratory of polymer physics and chemistry Institute of Chemistry Chinese Academy of Sciences Beijing 100080 Graduate School of the chinese academy of sciences Beijing 100080

^13C spin-lattice relaxation times （T1） of a conjugated polymer MEH-PPV in polymer/ layered silicate nanocomposites together with the steady state fluorescence emission and transient fluorescence decay measurements have been investigated. The T1 values of the conjugated carbons decrease dramatically according to the reduction of polymer concentration in the nano composites, while the fluorescence life times （τ） show a linear prolonging tendency. The results are explained from the point of view of molecular dynamics.

关键词： Conjugated polymer nanocomposites fluorescence solid state ^13C NMR

Synthesis of Exfoliated MEH-PPV /Clay Nanocomposites

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chinese Chemical Letters 2005年第8期16卷 1117-1120页

The synthesis of poly（2-methoxy-5-（2＇-ethyl-hexyloxy）-l,4-phenylenevinylene）（MEH-PPV） in the presence of organophilic montmorillonite （OMMT） was reported and the exfoliated MEH-PPV/OMMT nanocomposites was ob... 详细信息

关键词： MEH-PPV nanocomposite in-situ polymerization.

Engineering Spin states of Isolated Copper Species in a Metal-Organic Framework Improves Urea Electrosynthesis

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Nano-Micro Letters 2023年第9期15卷 536-549页

作者： Yuhang gao jingnan Wang Yijun Yang Jian Wang Chuang Zhang xi Wang Jiannian Yao key laboratory of Photochemistry Beijing National Laboratory for Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing 100190People’s Republic of China University of chinese academy of sciences Beijing 100049People’s Republic of China molecular Plus and Collaborative Innovation center of Chemical science and Engineering Tianjin UniversityTianjin 300072People’s Republic of China Department of physics School of Physical Science and EngineeringBeijing Jiaotong UniversityBeijing 100044People’s Republic of China Research center for Magnetic and Spintronic Materials National institute for Materials science Tsukuba 305-0047Japan

The catalytic activities are generally believed to be relevant to the electronic states of their active center, but understanding this relationship is usually difficult. Here, we design two types of catalysts for electrocatalytic urea via a coordination strategy in a metal–organic frameworks: Cu^(Ⅲ)-HHTP and Cu^(Ⅱ)-HHTP. Cu^(Ⅲ)-HHTP exhibits an improved urea production rate of 7.78 mmol h^(−1)g^(−1) and an enhanced Faradaic efficiency of 23.09% at-0.6 V vs. reversible hydrogen electrode, in sharp contrast to Cu^(Ⅱ)-*** CuⅢspecies with S = 0 spin ground state are demonstrated as the active center in Cu^(Ⅲ)-HHTP, different from Cu^(Ⅱ) with S = 1/2 in Cu^(Ⅱ)-HHTP. We further demonstrate that isolated Cu^(Ⅲ)with an empty dx2-y20orbital in Cu^(Ⅲ)-HHTP experiences a single-electron migration path with a lower energy barrier in the C–N coupling process, while Cu^(Ⅱ)with a single-spin state( d_(x2-y2)^(1)) in Cu^(Ⅱ)-HHTP undergoes a two-electron migration pathway.

关键词： Electrocatalysis Urea synthesis Metal-organic framework Spin catalysis C-N coupling

Coherent effects in a three-photon CPT process of Ca＋

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Frontiers of physics 2011年第3期6卷 258-261页

作者： Qu LIU Bao-quan OU xi-wen ZHU Ke-lin gao state key laboratory of Magnetic Resonance and Atornic and molecular physics Wuhan lnstitute of Physics and Mathematics （WIPM） Chinese Academy of Sciences （CAS） Wuhan 430071 China centers for Cold Atom physics CAS Wuhan 430071 China Graduate School of the chinese academy of sciences Beijing 100049 China Department of physics Science College National University of Defense Technology Changsha 410073 China

Linewidth narrowing and other quantum coherent effects based on three-photon coherent population trapping （CPT） in Ca＋ ions are investigated. If the propagation directions of the three lasers obey the phase matching condition, the dark linewidth resulting from the CPT can be very narrow, and it can be controlled by adjusting the parameters of the lasers.

关键词： coherent population trapping (CPT) linewidth coherent effects

The impact of reabsorption effect on composition analysis of organic semiconductors

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science china Materials 2024年第10期67卷 3124-3131页

作者： Bei Yang xiaoke Liu Li Wan Weixin Ni Ni Yang Jianhui Hou Feng gao Electronic and Photonic Materials(EFM) Department of PhysicsChemistry and Biology(IFM)Linkoping UniversityLinkoping SE-58183Sweden beijing National laboratory for molecular sciences State Key Laboratory of Polymer and ChemistryCAS Research/Education Center for Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing 100190China Max Planck institute of Microstructure Physic Halle 06120Germany

Reabsorption is one of the most fundamental optical phenomena,but it has rarely been considered in spectroscopy-based composition analysis for organic ***,we take four state-of-the-art organic solar cell(OSC)materials as examples,and systematically investigate the influence of reabsorption on photoluminescence emission and excitation spectra by both experimental studies and optical *** find that the overlap between absorption and emission spectra of these OSC materials is strong enough for them to be affected by the reabsorption effect,and the effect becomes more obvious between different species in the multi-components ***,three features of the reabsorption effect and the reabsorption strength are identified,with which we have successfully analyzed the composition in a range of OSC materials in both solution and solid-state *** work not only provides an important understanding of the largely overlooked feature of reabsorption in the widely used spectroscopic techniques but also offers an effective toolbox for the composition analysis of organic semiconductors.

关键词： reabsorption effect composition analysis organic solar cells non-fullerene acceptors organic semiconductors