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Lewis acid/base modulation in β-diiminate zinc-catalyzed switchable ring-opening polymerization of rac-lactide

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Science China Chemistry 2019年第4期62卷 475-478页

作者： Pan Zhang Minhui Zhao wenmin pang Changle Chen Hefei National Laboratory for Physical Sciences at the Microscale Chinese Academy of Sciences Key Laboratory of Soft Matter ChemistryDepartment of Polymer Science and Engineering University of Science and Technology of China

Two β-diiminate zinc complexes were prepared and found to show high activity and well-controlled catalytic behavior in the ring-opening polymerization of rac-lactide. Coordination of the Lewis acid to the zinc complexes completely terminated the polymerization. The coordinated Lewis acid was easily cleaved by using a Lewis base, so that the polymerization could ***, switchable polymerization could be realized by the subsequent addition of a Lewis acid and a Lewis base. This work provides a new strategy to control the ring-opening polymerization of rac-lactide.

关键词： ring-opening polymerization β-diimine zinc catalysts modulation

Polyolefin vitrimers bearing acetoacetate functionality

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Science China Chemistry 2024年第11期67卷 3861-3867页

作者： Zihao Wang Yue Liu wenmin pang Ao Chen Min Chen Chinese Academy of Sciences(CAS)Key Laboratory of Soft Matter Chemistry Department of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefei 230026China Institutes of Physical Science and Information Technology Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of EducationAnhui UniversityHefei 230601China

Polyolefin vitrimers are polymer networks bearing reversible covalent crosslinking points, enabling them to be reprocessed and recycled. In this contribution, a series of polyolefin vitrimers were designed based on the acetoacetate-functionalized polyolefin copolymers, which were produced through the direct copolymerization of ethylene with polar comonomers using a phosphinesulfonate palladium catalyst. The pendant acetoacetate group could mediate several characteristic reactions, such as the Michael addition reaction, ketone-amine condensation and metal coordination reaction. As such, structurally adjustable polyolefin vitrimers can be accessed by introducing various dynamic crosslinking bonds, including disulfide exchange, transamination of vinylogous urethane and labile metal coordination bond. The utilization of different crosslinking reactions and the mole ratio of crosslinkers significantly impact the material properties of the resultant polymers. Specifically, the generated polyolefin vitrimers demonstrated excellent reprocessability and closed-loop recycling properties. The study in this work provides an efficient strategy to access various polyolefin vitrimers.

关键词： polyolefin vitrimers acetoacetate group polar monomer olefin copolymerization

Positional Electronic Effects in Iminopyridine-N-oxide Nickel Catalyzed Ethylene Polymerization

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Chinese Journal of Chemistry 2021年第6期39卷 1683-1689页

作者： Mingjun Chi Ao Chen wenmin pang Chen Tan Changle Chen CAS Key Laboratory of Soft Matter Chemistry Hefei National Laboratory for Physical Sciences at the MicroscaleDepartment of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefeiAnhui 230026China Institutes of Physical Science and Information Technology Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of EducationAnhui UniversityHefeiAnhui 230026China

A series of dibenzhydryl-based iminopyridine-N-oxide ligands bearing a range of electron-donating or-withdrawing substituents(OMe,H;and NO_(2))and corresponding nickel pre-catalysts are prepared and *** substituents are installed at different positions on the ligand structure,including 4-position of the pyridine-N-oxide moiety(position X)and 4-position of the aniline moiety(position Y).These nickel pre-catalysts are highly active in ethylene polymerization with the addition of very little amount of aluminum cocatalysts,leading to the formation of polyethylenes with molecular weights of well above one ***-donating substituents make the catalysts sensitive to polymerization *** contrast,the catalysts bearing electron-withdrawing NO_(2) substituents show relatively steady performances at different *** importantly,we demonstrate that different substituents and different positions both play important roles in determining the properties of nickel *** provides an alternative strategy for the future design of high-performance polymerization catalyst.

关键词： Ethylene Polymerization Nickel lminopyridine-N-oxide Substituent effects

Double stimulus-responsive palladium catalysts for ethylene polymerization and copolymerization

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Chinese Chemical Letters 2024年第7期35卷 407-411页

作者： Hailong He Wenbing Wang wenmin pang Chen Zou Dan Peng CAS Key Laboratory of Soft Matter Chemistry Department of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefei National Laboratory for Physical Sciences at the MicroscaleHefei 230026China

The external stimulus response strategy has been evolved rapidly in the field of olefin *** this work,we modularly synthesized three types of double stimulus responsiveα-diimine palladium catalysts,combining redox regulation and other regulation together,such as light,Lewis acid and alkali *** catalytic activities and the molecular weight of polyethylene products can be regulated for 4 times in ethylene *** palladium complexes were also used for the copolymerization reaction of ethylene and polar monomers,such as methyl 10-undecylenate and methyl acrylate,effectively regulating the catalytic activities,the molecular weight and polar monomer incorporation of the prepared *** research on these dual-regulated palladium complexes makes full use of prepared catalysts and provides new inspirations for regulating olefin polymerization.

关键词： Dual-regulated Stimulus-responsive Palladium Ethylene polymerization Polar monomer

SiO_(2)-Supported Ni(II)and Fe(II)Catalysts Bearing Sodium-Sulfonate Group for Olefin Polymerization

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Chinese Journal of Chemistry 2022年第23期40卷 2773-2779页

作者： Yao Sun Quan Wang Yao Pan wenmin pang Chen Zou Min Chen CAS Key Laboratory of Soft Matter Chemistry Department of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefeiAnhui 230026China Institutes of Physical Science and Information Technology Anhui UniversityHefeiAnhui 230601China

Heterogeneous catalysts have been dominant for industrial polyolefin production,offering many distinct advantages,such as controlling the morphology of the polymer and preventing reactor *** this contribution,we designed several types of imine ligands bearing sodium-sulfonate ionic groups and the corresponding nickel/iron *** catalysts could be immobilized on SiO_(2)with strong affinity and high catalyst *** SiO_(2)-supported catalysts behaved better than their homogeneous counterparts during ethylene polymerization with extremely high activity(2.6×10^(4)kg·mol^(−1)·h^(−1))and high thermal *** addition,the supported nickel catalysts generated free-flowing polyethylene with high molecular weight(Mn up to 2.65×10^(3)kg·mol^(–1))and excellent morphology control,indicating no reactor fouling due to the leaching of ***,for copolymerization,immobilized nickel catalysts showed a higher tolerance of polar monomers,and the efficient copolymerization of ethylene with undecylenic acid was achieved with high activity(450 kg·mol^(−1)·h^(−1))and a high incorporation ratio(up to 12.3%).

关键词： Heterogeneous catalysis Nickel iron catalysts Sodium-sulfonate group Polymerization Copolymerization

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关于后现代思潮及其意义的再认识

中国农业银行武汉培训学院学报 2006年第3期 53-55页

作者：庞文敏中国农业银行武汉培训学院财务室湖北武汉430077

如何把握后现代主义的精神实质及其对中国文化建设的意义,在于如何正确认识后现代主义与现代性之间的内在矛盾关系,本文围绕这一问题进行了探讨,指出后现代主义并不像人们所片面以为的那样,是对现代性的线性的逆转或平面的倾覆,而是在... 详细信息

如何把握后现代主义的精神实质及其对中国文化建设的意义,在于如何正确认识后现代主义与现代性之间的内在矛盾关系,本文围绕这一问题进行了探讨,指出后现代主义并不像人们所片面以为的那样,是对现代性的线性的逆转或平面的倾覆,而是在现代性的基础上所展开的对现代性的矫正与纠偏,本质上是对现代性的拓展、深化和超越。文章结合这一问题,同时对这种错误认识背后所蕴涵的单面性的思维方式及其历史教训进行了总结检讨。

关键词：后现代主义现代性单面性思维

PCL/SiO_2杂化纳米相微结构与晶态成核生长特性

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Chinese Journal of Chemical Physics 2005年第6期18卷 1023-1028页

作者：聂康明庞文民王雨松鲁非朱清仁安徽大学化学化工学院材料系合肥230039 中国科学技术大学结构分析重点实验室合肥230026

应用扫描电子显微镜、广角X射线衍射和差示扫描量热手段研究了有机高分子/无机组分间以物理次价力(氢键)键合的高分子量PCL/SiO2杂化材料纳米相微结构和PCL高分子链在该微结构环境中的结晶成核生长特性及其影响因素.研究结果表明:杂化... 详细信息

应用扫描电子显微镜、广角X射线衍射和差示扫描量热手段研究了有机高分子/无机组分间以物理次价力(氢键)键合的高分子量PCL/SiO2杂化材料纳米相微结构和PCL高分子链在该微结构环境中的结晶成核生长特性及其影响因素.研究结果表明:杂化体系中高分子/无机组分间的微相分离尺度在纳米数量级,高分子微区的平均相畴尺寸在70nm左右,无机相形态呈现不规则的颗粒状.两相均匀分布程度与体系中组分间的氢键键合强度有关.PCL杂化后结晶度减小,对应的微晶尺寸明显改变,平衡熔点随无机组成含量的增加而下降.高分子链在晶核表面折叠形成结晶结构所需的能量增加.这一结果归因于无机非晶SiO2和键合强度的影响.

关键词：聚己内酯有机-无机杂化材料微结构结晶成核生长

基于投入产出模型的大型活动对举办地的经济影响——以广交会为例

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地理学报 2011年第4期66卷 487-503页

作者：罗秋菊庞嘉文靳文敏中山大学旅游学院广州510275 中山大学旅游发展与规划研究中心广州510275

事件活动的经济影响评估是国外近20年来的研究热点,然而近年来遭到很多质疑和争论,国内在该领域的理论和实证研究仍处于起步阶段。一年两届的广交会对举办城市具有持续的深远影响,是城市大型活动的典范。本研究以104与105届广交会为案例... 详细信息

事件活动的经济影响评估是国外近20年来的研究热点,然而近年来遭到很多质疑和争论,国内在该领域的理论和实证研究仍处于起步阶段。一年两届的广交会对举办城市具有持续的深远影响,是城市大型活动的典范。本研究以104与105届广交会为案例,采用问卷调查及深度访谈法收集广交会所有参与者的消费支出与结构,并运用投入产出模型评估广交会对广州市间接经济影响。结论表明城市定期举办的大型商务活动对举办地的许多产业部门具有很强的拉动效应,对当地经济产生明显的持续性的经济效应;一届广交会对广州市的直接与间接效应合计163.24亿元,其中直接经济效应55.26亿元,间接经济效应为107.98亿元,直接与间接效应之比为1:1.95;2008年104届广交会的直接与间接效应总和占广州市全年GDP的1.98%;参与者对广州的经济拉动作用依次为采购商、参展企业、参展个人、承办方、交易团。此外,本文还特别就研究结论存有高估或低估倾向进行了探究。

关键词：大型事件广交会广州直接经济影响间接经济影响投入产出模型

健康成年人肠道硫酸盐还原菌和丁酸盐产生菌的性别差异

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基因组学与应用生物学 2015年第9期34卷 1842-1847页

作者：冯舟李敏龙文敏庞小燕上海交通大学生命科学技术学院微生物代谢国家重点实验室上海200240

探究人体肠道内重要的功能菌——硫酸盐还原菌和丁酸盐产生菌在健康成年个体中的数量,并分析其与年龄、性别的关系。采集40名健康成年志愿者(男性:女性=1:1,年龄23~53岁)的粪便样品,采用试剂盒Invi Mag誖Stool DNA Kit联合Bead beating... 详细信息

探究人体肠道内重要的功能菌——硫酸盐还原菌和丁酸盐产生菌在健康成年个体中的数量,并分析其与年龄、性别的关系。采集40名健康成年志愿者(男性:女性=1:1,年龄23~53岁)的粪便样品,采用试剂盒Invi Mag誖Stool DNA Kit联合Bead beating的方法提取粪便中细菌总DNA。通过定量PCR技术对总菌、硫酸盐还原菌以及丁酸盐产生菌的拷贝数进行定量检测。结果显示,40名健康成年人每纳克粪便DNA中含有的细菌总量为(9.22×106±7.35×106)个拷贝,硫酸盐还原菌拷贝数为(9.21×103±9.87×103),而丁酸盐产生菌拷贝数稍高于硫酸盐还原菌,为(2.68×104±3.08×104)。硫酸盐还原菌和丁酸盐产生菌的数量在不同个体间存在较大差异。Spearman相关分析显示三类基因的拷贝数与志愿者年龄无显著相关关系。硫酸盐还原菌和丁酸盐产生菌的拷贝数及其相对丰度存在显著的性别差异,表现在男性个体含有更少的硫酸盐还原菌(p<0.05)和更多的丁酸盐产生菌(p<0.01)。本研究揭示了硫酸盐还原菌和丁酸盐产生菌在健康成年人肠道内的数量,为进一步探究肠道菌群的性别差异提供了新的思路。

关键词：肠道菌群性别差异定量PCR 硫酸盐还原菌丁酸盐产生菌