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Access to High-Molecular-Weight Polyethylenes through High Temperature Ethylene Polymerization Catalysed by Ethylene-Bridged ansa-(3-R-Cyclopentadienyl)(Fluorenyl) Zirconocene Complexes

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Chinese Journal of Polymer Science 2024年第1期42卷 42-51,I0007页

作者： Bo Li haiyan ma Jiling Huang Shanghai Key Laboratory of Functional materials Chemistry and Laboratory of Organometallic Chemistry School of Chemistry and Molecular EngineeringEast China University of Science and TechnologyShanghai 200237China

A series of C1-symmetric ethylene-bridged ansa-(3-R-cyclopentadienyl)(fluorenyl) metallocene complexes(Zr: 1-5;Hf: 6) have been synthesized, characterized and investigated as catalyst precursors for the high temperature ethylene polymerization. Using methylaluminoxane(maO) as the cocatalyst, zirconium complexes 1-5 bearing a bulky substituent on the 3-position of the cyclopendienyl ring showed high catalytic activities up to 1.48×10^(7) g PE·mol_(Zr)^(-1)·h^(-1) toward the polymerization of ethylene and afforded polyethylenes with high molecular weights(1.49×10^(5)-6.31×10^(5) g/mol), meanwhile exhibting great thermal stability at high temperatures up to 120 ℃ together with a long catalytic life time up to 2 h. By adopting low Al/Zr ratios, such as 125, polyethylenes with ultra high molecular weights up to 2.86×106 g/mol were obtained. It is worthy of noting that zirconium complexes 1-4 bearing a substituent with an aryl pendant showed temperature-dependent activities, which increased rapidly with the increase of polymerization temperature, thus weak interaction of the pendent aryl group with the cationic active center is proposed to account for the very low activities displayed at low temperatures. In contrast to zirconocene complexes 1-5, hafnocene complex 6 only displayed very low catalytic activities toward the polymerization of ethylene and afforded polyethylenes with molecular weights ten times smaller than those obtained by zirconocene complexes 1-5. Zirconocene complexes 1-5 were also able to catalyse the polymerization of propylene at high temperatures, but only afforded waxes with low molecular weights.

关键词： ansa-Metallocene Ethylene Propylene Polymerization High temperature

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Ethylene-bridged Indenyl-fluorenyl Metallocene Complexes for Efficient Preparation of Allyl-terminated Propylene Oligomers and Polymers via Selective β-Methyl Transfer

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Chinese Journal of Polymer Science 2019年第6期37卷 578-590页

作者： Lei Zhang Bin Zhang haiyan ma Shanghai Key Laboratory of Functional materials Chemistry and Laboratory of Organometallic Chemistry School of Chemistry and Molecular EngineeringEast China University of Science and Technology

Four C_1-symmetric ansa-metallocene complexes, C_2H_4(Ind)(2,7-~tBu_2-Flu)ZrCl_2(4), C_2H_4(3-Bn-Ind)(2,7-~tBu_2-Flu)ZrCl_2(5),C_2H_4(3-Bn-Ind)(3,6-~tBu_2-Flu)ZrCl_2(6), and C_2H_4(3-Bn-Ind)(2,7-~tBu_2-Flu)HfCl_2(7), were synthesized and characterized. The structures of complexes 4, 5, and 7 were further determined via X-ray diffraction studies. Upon activation with modified methylaluminoxane(MmaO) or Al^iBu_3/[Ph_3C][B(C_6F_5)_4](TIBA/TrB), most of these complexes showed high efficiency in catalyzing propylene oligomerization/polymerization to afford products dominantly with allyl terminals via selective β-methyl transfer(β-Me transfer). The introduction of 3-benzyl group on the indenyl ring of the complexes was found to be crucial in enabling highly selective β-Me transfer during the polymerization process, leading to selectivities up to 89% obtained by zirconocene complexes 5 and 6, and up to 91% obtained by hafnocene complex 7. Detailed chain-end analysis by ~1H-NMR, ^(13)C-NMR, and maLDI-TOF mass spectroscopy revealed that the allyl chain-ends of the polymeric products resulted from a selective β-Me transfer process after two successively primary insertions of the monomer. Further studies concerning the dependence of chain release selectivity as well as the molecular weight of products on monomer concentration suggested that both β-Me transfer(major) and β-hydrogen transfer(β-H transfer)(minor) mediated by 5/MmaO and 6/MmaO systems may mainly operate in a bimolecular pathway.

关键词： Metallocene Ethylene-bridged indenyl-fluorenyl ligand Propylene Oligo-/polymerization β-Methyl transfer

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Binuclear Aluminum Complexes Supported by Linked Bis(β-diketiminate) Ligands for Ring-Opening Polymerization of Cyclic Esters

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Chinese Journal of Polymer Science 2018年第2期36卷 190-201页

作者： Shaogang Gong Peng Du haiyan ma Shanghai Key Laboratory of Functional materials Chemistry and Laboratory of Organometallic Chemistry School of Chemistry and Molecular EngineeringEast China University of Science and Technology

Binuclear aluminum alkyl complexes 2a–4g supported by linked bis（β-diketiminate） ligands were synthesized via the reaction of AlEt3 or AlMe3 and the corresponding proligand in a 2：1 molar ratio with moderate yields. The isolated complexes were well-characterized by ^1H-NMR, ^13C-NMR and elemental analysis. The binuclear nature of aluminum complex 2b was further confirmed by an X-ray diffraction study. All complexes 2a–4g could efficiently initiate the ring-opening polymerization（ROP） of ε-caprolactone in toluene. The substituents at the aromatic rings and the linker unit in the auxiliary ligands exerted significant influence on the catalytic behavior of the investigated aluminum complexes. Complex 4g（R^1 = R^2 = Cl） containing propylenyl bridging unit exhibited the highest catalytic activity among these complexes, which might be attributed to the increased electrophilicity of the metal center as well as more opened coordination sphere. The molecular weights of obtained poly（ε-caprolactone）s deviating considerably from the theoretical values indicated that the ROP of ε-caprolactone by complexes 2a–4g was not well-controlled, which was also judged from the broad molecular weight distributions（MWD = 1.47-2.47） of produced poly（ε-caprolactone）s. These complexes proved to be inactive toward the polymerization of rac-lactide alone. In the presence of alcohol the polymerization occurred, which was actually initiated by the decomposition species of the aluminum complex upon the treatment with isopropanol.

关键词： Bis(β-diketiminate) ligand Aluminum complex Binuclear Polymerization Cyclic ester

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Brine-freeze-thaw Durability and Crack Density Model of Concrete in Salt Lake Region

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Journal of Wuhan University of Technology(materials Science) 2020年第3期35卷 561-570页

作者： GONG Wei YU Hongfa ma haiyan HAN Wenliang Department of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The brine-freeze-thaw durability (defined as the durability under freeze-thaw cycles in Qinghai salt lake brine) of concrete (ordinary Portland cement concrete (OPC), high performance concrete (HPC-a), high performance concrete with steel fiber (HPC-b), and high performance concrete with high Young's modulus polyethylene fiber (HPC-c)) was systematically investigated by the relative dynamic elastic modulus, the relative mass, the appearance, the scanning electron microscopy, and the X-ray diffraction. In addition, the low-temperature physical and chemical corrosion mechanism and a crack density model after the modified relative dynamic elastic modulus being taken into consideration were proposed. The results show that the deterioration of OPC is the severest, followed by HPC-a, HPC-c and HPC-b. The admixture or the fiber is mixed into concrete, which can improve the brine-freeze-thaw durability of concrete. The critical mass growth of the failure of concrete is 3.7%. The cause of the deterioration of concrete under the brine-freeze-thaw cycles is physical and chemical corrosion, not freezing and thawing. The crack density model can effectively describe the deterioration evolution of concrete.

关键词： brine-freeze-thaw durability relative dynamic elastic modulus relative mass micro-analysis modeling

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Dynamic Impact Compressive Behavior Investigation of Sisal Fiber-reinforced Coral Seawater Concrete

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Journal of Wuhan University of Technology(materials Science) 2023年第5期38卷 1034-1043页

作者： ma haiyan TAN Yongshan YU Hongfa YUE Chengjun ZHANG Yan Department of Airport and Civil Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China College of Civil Science and Engineering Yangzhou UniversityYangzhou 225i27China School of Civil Engineering Southeast UniversityNanjing 21118China

Split Hopkinson pressure bar(SHPB)was used to investigate the dynamic compressive properties of sisal fiber reinforced coral aggregate concrete(SFCAC).The results showed that,with the increase of strain rate,the dynamic compressive strength,peak strain and toughness index of SFCAC are all greater than its static properties,indicating that SFCAC is a kind of rate-sensitive *** the sisal fiber was blended,the failure mode showed obvious *** high strain rates,the SFCAC without sisal fiber specimen was comminuted,and the SFCAC showed a"cracked without breaking"*** results indicated that the sisal fiber played a significant role in reinforcing and strengthening the properties of *** finite element software LS-DYNA was used to simulate two working conditions with strain rates of 78 and 101 *** stressstrain curves and failure patterns obtained were in good agreement with the experimental results.

关键词： coral aggregate concrete sisal fiber dynamic compressive strain-rate effect

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Towards SDN Based Queuing Delay Estimation

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China Communications 2016年第3期13卷 27-36页

作者： ma haiyan YAN Jinyao Panagiotis Georgopoulos Bernhard Plattner Faculty of Science and Technology Communication University of China Computer Engineering and Networks Laboratory Swiss Federal Institute of Technology Zurich (ETH Zurich)

As one of Qo S(Quality of Service) metrics, delay is critical important to delay sensitive applications, such as interactive video, network game and online surgery. In this paper, we exploit SDN(Software Defined Networking) advantages to solve delay Qo S problem. Our work mainly focuses on SDN based queuing delay estimation with real traffic and end-to-end delay control. First, we propose a queuing estimation model and extended it for end-to-end delay of the whole path. It is proved to be feasible and accurate with experimental results in SDN environment. Second, in order to demonstrate the use of our proposed model, we also implement an end-to-end delay control application in SDN. It fulfills specific delay Qo S requirements by dynamically switching flows to a suitable queue based on estimation results and delay requirements.

关键词： autonomic Qo S dynamic model delay performance SDN

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Mesoscopic Modeling Approach and Application for Steel Fiber Reinforced Concrete under Dynamic Loading:A Review

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Engineering 2022年第9期16卷 220-238页

作者： Jinhua Zhang Zhangyu Wu Hongfa Yu haiyan ma Bo Da School of Civil Engineering Southeast UniversityNanjing 210096China Department of Civil and Airport Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Science and Technology on Near-Surface Detection Laboratory Wuxi 214035China College of Harbour Coastal and Offshore EngineeringHohai UniversityNanjing 210098China

Steel fiber reinforced concrete(SFRC)has drawn extensive attention in recent years for its superior mechanical response to dynamic and impact *** on the existing test results,the highstrength steel fibers embedded in a concrete matrix usually play a strong bridging effect to enhance the bonding force between fiber and the matrix,and directly contribute to the improvement of the post-cracking behavior and residual strength of *** gain a better understanding of the action behavior of steel fibers in matrix and further capture the failure mechanism of SFRC under dynamic loads,the mesoscopic modeling approach that assumes SFRC to be composed of different mesoscale phases(i.e.,steel fibers,coarse aggregates,mortar matrix,and interfacial transition zone(ITZ))has been widely employed to simulate the dynamic responses of SFRC material and structural *** paper presents a comprehensive review of the state-of-the-art mesoscopic models and simulations for SFRC under dynamic *** approaches for the SFRC mesoscale model in the simulation works,including steel fiber,coarse aggregate,and the ITZ between them,are reviewed and compared *** material models for different phases and the interaction relationship between fiber and concrete matrix are summarized ***,some example applications for SFRC under dynamic loads(i.e.,compression,tension,and contact blast)simulated using the general mesoscale models are ***,some critical analysis on the current shortcomings of the mesoscale modeling of SFRC is highlighted,which is of great significance for the future investigation and development of SFRC.

关键词： Steel fiber reinforced concrete Mesoscale modeling Dynamic loading materials model Interfacial characteristic

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Compressive Strength of Basic magnesium Sulfate Cement Coral Aggregate Concrete(MCAC)on Non-Destructive Testing

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Journal of Wuhan University of Technology(materials Science) 2023年第5期38卷 1086-1095页

作者： GUO Jianbo YU Hongfa ma haiyan CHANG Yun MEI Qiquan ZHANG Yan Department of Civil and Airport Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China School of Architectural Engineering Nanjing University of EngineeringNanjing 210009China

Basic magnesium sulfate cement coral aggregate concrete(MCAC)is a new type of concrete consisting of basic magnesium sulfate cement,coarse coral aggregate,coral reef sand and *** rebound hammer(RH),the ultrasonic pulse velocity(UPV)and the compressive strength(fcu)tests of 14 sets of cube specimens of the MCAC after 28 d of aging were *** impact of the content and length of sisal fiber on the relationship between the fcu-RH and the fcu-UPV was determined.A mathematical model was established to predict the strength of the MCAC using the UPV,RH,and comprehensive UPV/RH methods and to obtain the curves of test *** applicability of the test strength curves of ordinary portland concrete(OPC),light-weight aggregate concrete(LAC),and coral aggregate concrete(CAC)to MCAC was *** results showed that the test strength curves of OPC,LAC and CAC were inappropriate to determine the strength of MCAC using non-destructive *** relative standard error of the curves of test strength of the RH method and the comprehensive method met the specifications,whereas that of the UPV method did not.

关键词： non-destructive testing basic magnesium sulfate cement coral aggregate corcrete ultrasonic pulse velocity rebound hammer specific test strength curves

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Ability of multicellular salt glands in Tamarix species to secrete Na^+ and K^+ selectively

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Science China(Life Sciences) 2011年第3期54卷 282-289页

作者： ma haiyan TIAN ChangYan FENG Gu YUAN JunFeng Xinjiang Instttute of Ecology and Geography Key Laboratory of Oasis Ecology and Desert Chinese Academy of Sciences Urumqi 830011 China Graduate University of Chinese Academy of Sciences Beijing 100039 China College of Resources and Environmental Sciences China Agricultural University Beijing 100094 China

The present study aimed to determine the mechanism of cation-selective secretion by multicellular salt *** a hydroponic culture system,the secretion and accumulation of Na+ and K+ in Tamarix ramosissima and *** under different salt stresses (NaCl,KCl and NaCl+KCl) were ***,the effects of salt gland inhibitors (orthovanadate,Ba2+,ouabain,tetraethylammonium (TEA) and verapamil) on Na+ and K+ secretion and accumulation were *** with NaCl (at 0-200 mmol L 1 levels) significantly increased Na+ secretion,whereas KCl treatment (at 0-200 mmol L 1 levels) significantly increased K+ *** ratio of secretion to accumulation of Na+ was higher than that of K+.The changes in Na+ and K+ secretion differed after adding different ions into the single-salt *** of NaCl to the KCl solution (at 100 mmol L 1 level,respectively) led to a significant decrease in K+ secretion rate,whereas addition of KCl to the NaCl solution (at 100 mmol L 1 level,respectively) had little impact on the Na+ secretion *** results indicated that Na+ secretion in Tamarix was highly *** addition,Na+ secretion was significantly inhibited by orthovanadate,ouabain,TEA and verapamil,and K+ secretion was significantly inhibited by ouabain,TEA and *** different impacts of orthovanadate on Na+ and K+ secretion might be the primary cause for the different Na+ and K+ secretion abilities of multicellular salt glands in Tamarix.

关键词： Tamarix salt gland inhibitor ion secretion salt stress

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Three-Dimensional Mesoscopic Investigation on the Impact of Specimen Geometry and Bearing Strip Size on the Splitting-Tensile Properties of Coral Aggregate Concrete

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Engineering 2022年第10期17卷 110-122页

作者： Zhangyu Wu Jinhua Zhang Hongfa Yu Qin Fang haiyan ma Li Chen Department of Civil and Airport Engineering Civil Aviation CollegeNanjing University of Aeronautics and AstronauticsNanjing 210016China School of Civil Engineering Southeast UniversityNanjing 210096China Engineering Research Center of Safety and Protection of Explosion and Impact of Ministry of Education(ERCSPEIME) Southeast UniversityNanjing 211189China Army Engineering University of PLA Nanjing 210007China

The use of coral aggregate concrete(CAC)as a novel construction material has attracted significant attention for the construction of reef engineering *** investigate the static splitting-tensile behaviors of CAC under the influence of two factors,namely specimen geometry and bearing strip size,a three-dimensional(3D)mesoscale modeling approach with consideration for aggregate randomness in shape and distribution was adopted in this *** established 12 different specimen models with two specimen shapes(i.e.,a cube with an edge length of 150 mm and a cylinder with dimensions ofφ150 mm×300 mm)and six strip widths(i.e.,6,9,12,15,18,and 20 mm)for *** effects of specimen geometry and strip width on the splitting-tensile properties of CAC,such as failure processes,final failure patterns,and splitting-tensile strength(fst),are analyzed and discussed *** results indicate the high reliability of the developed mesoscale modeling approach and reveal the optimal computational parameters for simulating and predicting the splitting-tensile properties of *** fstvalues of CAC are associated with both the specimen geometry and width of the bearing *** fstvalues of the cube model are slightly higher than those of the cylinder model for the same bearing strip size,representing geometry effects that can be explained by differences in fracture ***,the fstvalue of CAC gradually increases with the relative width of the bearing strip ranging from 0.04 to *** on the elastic solution theory,the variation area of CAC fstvalues with the relative width of the bearing strip was determined preliminarily,which has great significance for studying the tensile performance of CAC.

关键词： Coral aggregate concrete 3D mesoscopic modelling Splitting-tensile test Tensile strength Specimen geometry Bearing strip

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