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IMPACT PROPERTIES OF METALLOCENE - CATALYZED ETHYLENE-α-OLEFIN COpolymerS

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Chinese Journal of polymer science 2002年第5期20卷 473-480页

作者： Xu-rong Xu Jun-ting Xu lin-xian feng department of polymer science and engineering zhejiang university hangzhou 310027,china department of polymer science and engineering College of Chemistry & Molecular engineering Peking university Beijing 100871, china zhejiang Univ Dept Polymer Sci & Engn Hangzhou 310027 Peoples R China Peking Univ Coll Chem & Mol Engn Dept Polymer Sci & Engn Beijing 100871 Peoples R China

The impact properties of two selected metallocene-catalyzed ethylene-butene copolymers and one conventionalcopolymer were evaluated using Izod impact test. It is found that the metallocene-catalyzed copolymer shows superior impactproperties. This result was explained on the basis of the more homogeneous inter-molecular composition distribution andnarrower molecular weight distribution, which leads to more homogeneous morphology with fewer defects. Stepwisecrystallization improves the impact properties, especially in the crack propagation process, to a large extent. This is due to thedecrease of entanglements by stepwise crystallization, which is advantageous for the chain slip and shear. The polymer withheterogeneous intra-molecular composition distribution exhibits a more evident improvement of impact properties understepwise crystallization.

关键词： Metallocene-catalyzed ethylene-butene copolymer Impact properties Molecular heterogeneities Thermal treatment

polymerIZATION OF γ-STEARYL-α,l-GLUTAMATE N-CARBOXYANHYDRIDE USING RARE EARTH COORDINATION CATALYSTS

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Chinese Journal of polymer science 2000年第4期18卷 369-372页

作者： Xiao-ping Hu Jian Wu Zhi-kang Xu lin-xian feng Institute of polymer science, zhejiang university, hangzhou 310027, china department of Chemistry, zhejiang university, hangzhou 310027, china zhejiang Univ Dept Chem Hangzhou 310027 Peoples R China zhejiang Univ Inst Polymer Sci Hangzhou 310027 Peoples R China

A rare earth coordination system was first investigated as a new type of catalyst for the ring-openingpolymerization of α-amino acid N-carboxyanhydrides (NCAs). The results for the polymerization of γ-stearyl-α,L-glutamate(SLG) NCA using neodymium acetylacetonate (Nd(acac)_3)- or neodymium tris(2-ethylhexylphosphonate) (Nd(P_(204))_3)-triethylaluminum-water as catalysts were compared with those using conventional catalysts. It was found that the helicalpoly(γ-stearyl-L-glutamate) with high molecular weight as well as narrow molecular weight distribution can be obtained inthe presence of Nd(acac)_3/AlEt_3-1/2H_2O. The polymer obtained was characterized by IR and NMR spectroscopy.

关键词： Rare earth coordination catalyst Ring-opening polymerization Polypeptide Poly(γ-stearyl-α,L-glutamate)

Effect of polymerization Temperature on Propylene polymerization with C_s-symmetric Metallocene Catalyst

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Chinese Chemical Letters 2000年第2期11卷 167-170页

作者： Zhi Qiang FAN Tariq YASIN lin xian feng (department of polymer science and engineering, zhejiang university, hangzhou 310027) zhejiang Univ Dept Polymer Sci & Engn Hangzhou 310027 Peoples R China

A novel highly active C-s-symmetric metallocene catalyst namely: meso-dimethylsilylbis (2,4,6-trimethyl-1 -indenyl)zirconium dichloride is presented. The effect of polymerization temperature (0-70 degrees C) on the catalyst performance for propylene polymerization has been investigated. This catalyst shows very high activity at 50 degrees C which is higher than the activity of the racemic analogue, and the resulted polypropylene is amorphous in nature with isotactic pentad content [mmmm] of 12 %.

关键词： polymerization metallocene catalyst propylene

Effects of Al(i-Bu)_3 on Propylene polymerization and Copolymerization by rac-Me_2Si(Ind)_2ZrCl_2/MAO

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Chinese Chemical Letters 1998年第1期9卷 83-85页

作者： Zhi Qiang FAN Yong Hui ZHANG Qi WANG lin xian feng (department of polymer science and engineering, zhejiang university, hangzhou 310027) zhejiang Univ Dept Polymer Sci & Engn Hangzhou 310027 Peoples R China

The effects of adding Al(i-C_4H_9)_3 (TBA) to rac-Me2Si(Ind)2ZrCl2/ MAO catalyzed propylene-1-octene copolymerization were studied. At TBA /MAO (Al/AI mole ratio) of about 0.6, the polymerization activity was found to be much higher than the system without TBA. Increases of polymer molecular weight and 1-octene content from addition of TBA were also observed.

关键词： propylene-1-octene polymerization metallocene catalyst

SYNTHESIS OF NOVEL THIOPHENEDIMETHYLENE BRIDGED HOMOBINUCLEAR METALLOCENES AND THEIR CATALYTIC PROPERTIES FOR ETHYLENE polymerIZATION

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Chinese Journal of polymer science 2006年第1期24卷 21-27页

作者： Xi-jie Liu Jun-quan Sun Hai-ying Zhang Xiao-hui Xiao and feng lin department of Chemical engineering,College of Material and Chemical engineering,zhejiang university,hangzhou 310027,china zhejiang Univ Coll Mat & Chem Engn Dept Chem Engn Hangzhou 310027 Peoples R China

By treating disodium（thiophenedimethylene）dicyclopentadienide C4H2S（CH2C5H4Na）2 with two equivalent of CpTiCl3 or CpZrC13 DME at 0℃ in THF, two new thiophenedimethylene bridged binuclear metallocenes [Cl2MC5H5][C5H4CH2C4H2SCH2C5H4][C5H5MCl2] （M = Ti 3, M = Zr 4） were synthesized in high yield and their structures were characterized by ^1H-NMR. These complexes were used as catalysts for ethylene polymerization in the presence of methylaluminoxane （MAO）. The effects of polymerization temperature, time, concentration of catalyst, molar ratio of MAO/Cat on polymerization were studied in detail. The catalytic activities of thiophenedimethylene bridged binuclear metallocene catalysts （3, 4） reached 2.44 × 10^5 g PE mol^-1 cat^-1· h^-1, 9.61 × 10^5 g PE mol^-1 · cat^-1· h^-1 respectively, which are higher than that of pheneyldimethylene bridged binuclear metallocene catalysts and much higher than that of corresponding mononuclear metallocenes （Cp2TiCl2 and Cp2ZrCl2）. The molecular weight distribution curves of polyethylenes produced by binuclear metallocene catalysts （3, 4） and by mononuclear metallocene catalyst have only single peak, but the former （MWD = 3.5-4.7） is obviously broader than the latter （MWD = 2.0-2.2）.

关键词： Binuclear metallocene Thiophenedimethylene bridged Ethylene polymerization.

Synthesis, Purification and Characterization of Amphiphilic and Microphase Separated Graft Copolymer Polystyrene-g-Poly(ethylene oxide)

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Chemical Research in Chinese Universities 1992年第3期8卷 278-286页

作者： QIU Yong-xing, YU Xiao-jie, feng lin-xian and YANG Shi-lin (department of polymer science and engineering, zhejiang university, hangzhou)

The present paper covers the poly (ethylene oxide) macromer with vinyl benzyl terminal group (PEO-VB) prepared by deactivation of the alkoxide function of mono-functional 'living' PEO chains with vinyl benzyl chloride (VBC). The obtained macromers were subjected to careful purification and detailed characterization. A new kind of amphiphilic polystyrene-g-poly(ethylene oxide) (PS-g-PEO) with both mi-crophase separated and PEO side chains was synthesized from radical copolymerization of PEO-VB macromer with styrene monomer. An improved purification method, referred as 'selective dissolvation', was established for the isolation of graft copolymers from the grafting products, and the purity and yield of the purified copolymers were satisfactory. The well-defined structure of the purified copolymers was confirmed by IR, 1H NMR and GPC. The bulk composition of the graft copolymers was determined by a well-established first derivative UV spectrometry. Various experimental parameters controlling the copolymerization were also studied. The results indicate that the feed ratio of macromer to styrene (M/S) was the most important factor in determining the composition of the copolymers. Thus a series of PS-g-PEO with a wide range of bulk compositions were obtained simply by adjusting the value of M/S. As clearly indicated by transmission electron microscopy, this amphiphilic graft copolymers may readily form microphase separated structures.

关键词： Poly(ethyiene oxide) macromer Polystyrene-g-poly(ethylene oxide) Pu-rification of graft copolymer Amphiphilic and microphase separated structure Biocom-patible polymer

Syntheses of Substituted Indan-1-onesand Indenes

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Chemical Research in Chinese Universities 1999年第3期15卷 281-285页

作者： YASIN Tariq FAN Zhi-qiang feng lin-xian department of polymer science and engineering Zhejiang UniversityHangzhou 310027P.R.China

The syntheses of three novel substituted indanones namely 2,7 dimethylindan 1 one, 2 methyl 4,7 diethylindan 1 one and 2,4 dimethyl 7 methoxyindan 1 one are described. These indanones were prepared by different routes involving intramolecular ring closure of aryl substituted compounds by Friedel Crafts reaction. The t butyl was used as the positional protective group in the selective preparation of 2,7 dimethylindan 1 one. The corresponding indenes were prepared by reduction and dehydration reactions from these indanones.

关键词： Friedel Crafts reaction 1 Indanone Substituted indene

Propylene polymerization Catalyzed by Bis(R_3-indenyl) Zirconium Bichloride/Aluminoxane──Synthesis of Metallocenes and Influence ofSolvent Polarity on polymerization

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Chemical Research in Chinese Universities 2001年第4期17卷 445-451页

作者： YASIN Tariq FAN Zhi-qiang ZHU Yin-bang feng lin-xian department of polymer science and engineering Zhe Jiang UniversityHangzhou 310027China

Three unbridged metallocenes, bis(2,4,7-Me3-indenyl)zirconium dichloride(1) , bis(2-Me-4, 7-Et2-indenyl)zirconium dichloride (2) and bis (2, 4, 6-Me3-indenyl) zirconium dichloride (3) were synthesized. The effect of solvent polarity on propylene polymerization catalyzed by the metallocenes in the presence of methylaluminoxane(MAO) and triisobutylaluminum(TIBA) was investigated in the toluene/CH2Cl2 mixed solvent. Changing the solvent polarity was found to influence the catalytic activity, polymer molecular weight and stereospecificity of the catalysts. The changes in the position of the substituents on the ligand caused the different responses of the catalyst to the changes in solvent polarity. The isotactic stereosequence of polypropylene was found to increase with the increase in the polarity of the reaction medium.

关键词： Propylene polymerization Metallocene catalyst Solvent effect Polarity

Microneedle-array patch with pH-sensitive formulation for glucoseresponsive insulin delivery

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Nano Research 2021年第8期14卷 2689-2696页

作者： feng-Qin Luo Guojun Chen Wei Xu Daojia Zhou Jia-xian Li Yong-Cong Huang Run lin Zhen Gu Jin-Zhi Du Guangzhou First People’s Hospital and Institutes for Life SciencesSchool of MedicineSouth China University of TechnologyGuangzhou 510006China department of Bioengineering University of CaliforniaLos AngelesLos AngelesCA 90095-1413USA School of Biomedical sciences and engineering Guangzhou International Campus South China University of TechnologyGuangzhou 510006China department of Radiology the First Affiliated Hospital of Sun Yat-Sen UniversityGuangzhou 510080China National engineering Research Center for Tissue Restoration and Reconstruction Key Laboratory of Biomedical Materials and Engineering of the Ministry of EducationKey Laboratory of Biomedical Engineering of Guangdong ProvinceInnovation Center for Tissue Restoration and ReconstructionSouth China University of TechnologyGuangzhou 510006China Bioland Laboratory(Guangzhou Regenerative Medicine and Health Guangdong Laboratory) Guangzhou 510005China College of Pharmaceutical sciences Zhejiang UniversityHangzhou 310058China

Glucose-responsive insulin delivery systems show great promise to improve therapeutic outcomes and quality of life for people with ***,a new microneedle-array patch containing pH-sensitive insulin-loaded nanoparticles(NPs)(SNP(I))together with glucose oxidase(GOx)-and catalase(CAT)-loaded pH-insensitive NPs(iSNP(G+C))is constructed for transcutaneous glucose-responsive insulin ***(I)are prepared via double emulsion from a pH-sensitive amphiphilic block copolymer,and undergo rapid dissociation to promote insulin release at a mild acidic environment induced by GOx in iSNP(G+C)under hyperglycemic *** in iSNP(G+C)can further consume excess H_(2)O_(2) generated during GOx oxidation,and thus reduce the risk of inflammation toward the normal *** in vivo study on type 1 diabetic mice demonstrates that the platform can effectively regulate blood glucose levels within normal ranges for a prolonged period.

关键词： drug delivery diabetes glucose-responsive pH-sensitive microneedle