共查询到20条相似文献,搜索用时 12 毫秒
1.
Weiwei Zuo Wen‐Hua Sun Shu Zhang Peng Hao Akinobu Shiga 《Journal of polymer science. Part A, Polymer chemistry》2007,45(15):3415-3430
A catalytic system of new titanium complexes with methylaluminoxane (MAO) was found to effectively polymerize ethylene for high molecular weight polyethylene as well as highly active copolymerization of ethylene and norbornene. The bis (imino‐indolide)titanium dichlorides (L2TiCl2, 1 – 5 ), were prepared by the reaction of N‐((3‐chloro‐1H‐indol‐2‐yl)methylene)benzenamines with TiCl4, and characterized by elemental analysis, 1H and 13C NMR spectroscopy. The solid‐state structures of 1 and 4 were determined by X‐ray diffraction analysis to reveal the six‐coordinated distorted octahedral geometry around the titanium atom with a pair of chlorides and ligands in cis‐forms. Upon activation by MAO, the complexes showed high activity for homopolymerization of ethylene and copolymerization of ethylene and norbornene. A positive “comonomer effect” was observed for copolymerization of ethylene and norbornene. Both experimental observations and paired interaction orbital (PIO) calculations indicated that the titanium complexes with electron‐withdrawing groups in ligands performed higher catalytic activities than those possessing electron‐donating groups. Relying on different complexes and reaction conditions, the resultant polyethylenes had the molecular weights Mw in the range of 200–2800 kg/mol. The influences on both catalytic activity and polyethylene molecular weights have been carefully checked with the nature of complexes and reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3415–3430, 2007 相似文献
2.
The activity of the transition metal complex, such as Ni(2-ethyl hexanoate)2 (1), Co(2-ethyl hexanoate)2 (2), TiCl4 (3), or CpTiCl3 (4) (Cp = cyclopentadiene), in combination with MAO (methylaluminoxane), was investigated in the polymerization of norbornene. The Ni(II) complex 1 with MAO showed moderate activity to give 20.8 kgpolymer/molNi h, while the other three complexes 2-4 with MAO just showed trivial activity. Effects of the Lewis acids on the activation of the catalyst of 1/MAO were examined. The employment of B(C6F5)3 with 1/MAO significantly enhanced the activity to give up to around 133 kgpolymer/molNi h. The use of other borane compounds, such as B(C6H5)3 and BEt3, or the stronger electron acceptor BF3 · OBu2, with 1/MAO in place of B(C6F5)3 clearly showed the main functions of B(C6F5)3. The high Lewis acidity of B(C6F5)3 enabled it to develop matured active complexes, thus enhancing the activity. Several Ni(II) complexes were employed to determine whether their activity was comparable to that of complex 1 in norbornene polymerization. The study of the 1H and 13C NMR spectra of the polynorbornene produced with 1/B(C6F5)3/MAO showed that the initiation of addition polymerization occurred through the insertion of the exo face of the norbornene into the active complex. Effects of the variation in the polymerization variables, such as the levels of B(C6F5)3 and MAO, temperature, and solvent, on the polymerization were discussed. 相似文献
3.
Dong‐Po Song Hong‐Liang Mu Xin‐Cui Shi Yan‐Guo Li Yue‐Sheng Li 《Journal of polymer science. Part A, Polymer chemistry》2012,50(3):562-570
The facile and efficient functionalization of polynorbornene has been achieved through direct copolymerization of norbornene (NB) with 5‐norbornene‐2‐yl acetate (NBA) or 5‐norbornene‐2‐methanol (NBM) using a series of β‐ketiminato Ni(II)‐Me pyridine complexes 1–4 (Scheme 2 ) in the presence of B(C6F5)3. Remarkably, the monomer conversion could reach up to about 96% in 10 min in the NB/NBA copolymerization. The copolymers with wide NBA contents (3.3–38.4 mol %) were obtained by variation of reaction conditions. These copolymers have high molecular weights (MWs) (Mn = 41.8–144 kg/mol) and narrow MW distributions (Mw/Mn = 1.80–2.27). In the absence of alkyl aluminum compounds, a monomer conversion of 81% was observed in the NB/NBM copolymerization, and copolymers with NBM content in the range of 11.2–21.8 mol % were obtained by variation of reaction conditions. In addition, Ni(II)‐Me pyridine complexes 2 was very active at a low B/Ni molar ratio of 6, while bis‐ligand complex 6 bearing the same ligand just showed moderate efficiency at a high B/Ni molar ratio of 20. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
4.
Sapanna Chaimongkolkunasin Xiaohua Hou Kotohiro Nomura 《Journal of polymer science. Part A, Polymer chemistry》2017,55(18):3067-3074
Ring opening metathesis polymerizations (ROMP) of norbornene (NBE), tetracyclododecene (TCD) in the presence of cis-cyclooctene (COE) using vanadium-alkylidene catalyst, V(CHSiMe3)(N-2,6-Cl2C6H3)(OC6F5)(PMe3)2 ( 1 ), were explored. The polymerizations with TCD afforded high-molecular-weight polymers (Mn = 19,500–47,400) with low PDI (Mw/Mn) values (1.18–1.38) which possess microstructure of repeated ring-opened TCD and certain methylene units by incorporation of ring-opened COE on the basis of microstructure analysis by NMR spectra and DSC thermograms; hydrogenated copolymer possessed melting temperature at 294 °C. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3067–3074 相似文献
5.
Binyuan Liu Yang Li Boo‐Gyo Shin Do Yeung Yoon IL Kim Li Zhang Weidong Yan 《Journal of polymer science. Part A, Polymer chemistry》2007,45(15):3391-3399
Three novel functionalized polynorbornenes (PNB) with pendant dimethyl carboxylate group (carboxylates—acetate, propionate, and butyrate) are synthesized as a vinyl‐type with a palladium (II) catalyst in high yield. The effects of size of substitutents, molar ratio of monomer to catalyst, solvent polarity, reaction time, and temperature on the polymerization of exo‐norbornene dimethyl propionate were systematically investigated. The low molar ratio and temperature, as well as high polarity of solvent, and long reaction time, are favorable for the enhancement of the monomer conversion, especially, the solvent have an obvious effect on the catalyst activity. The resulting poly(cis‐norbornene‐exo‐2,3‐dimethyl carboxylates) (PNB‐dimethyl carboxylates) show good solubility in common organic solvent and high thermal stability up to 360 °C. The glass transition temperature was detected by DMA at 331, 324, and 318 °C for acetate, propionate, and butyrate, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3391–3399, 2007 相似文献
6.
Marc D. Walter Rebecca A. Moorhouse Peter S. White Maurice Brookhart 《Journal of polymer science. Part A, Polymer chemistry》2009,47(10):2560-2573
Several cationic (allyl)Ni(II) complexes were synthesized and shown to be highly active for (2,3)‐vinyl addition polymerization of norbornene to yield polymers with low molecular weight distributions (MWDs) ranging from 1.4–1.9. In all cases slow initiation was followed by rapid propagation which prevents molecular weight control of the poly(norbornene). One of the intermediates in the polymerization process has been identified and characterized by NMR spectroscopy as the first insertion product resulting from the insertion of norbornene into the Ni? C allyl bond in cis‐exo fashion. This insertion product was synthesized independently and NMR studies showed that the first insertion of norbornene into the Ni? C allyl bond is a reversible process. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2560–2573, 2009 相似文献
7.
研究了[Ru(bpy)3]2+溶液中引入纳米银粒子的光谱学性质变化规律以及[Ru(bpy)3]2+与纳米银粒子所构成的溶液体系([Ru(bpy)3]2+-Ag)的电解质效应.研究结果表明,[Ru(bpy)3]2+吸附在纳米银粒子表面使纳米银粒子相互桥连形成规则的类链状网络聚集体.纳米银粒子造成[Ru(bpy)3]2+溶液荧光猝灭,且大尺寸的纳米银粒子引起的荧光猝灭程度较大.在[Ru(bpy)3]2+-Ag体系中引入电解质造成纳米银粒子不同程度的聚集和生长.电解质对纳米银聚集影响为:CaCl2MgCl2Ca(NO3)2KClKNO3.随着[Ru(bpy)3]2+-Ag体系中引入电解质含量的增加,溶液的荧光强度先降低而后又逐渐增强,直至达到定值,表明一定量的电解质可产生荧光猝灭释放效应.电解质对荧光强度影响顺序为:Ca(NO3)2CaCl2MgCl2KClKNO3.采用透射电子显微镜、紫外-可见吸收分光光度计和荧光分光光度计等手段从分子间相互作用和能量传输等方面初步探讨了纳米银粒子对表面吸附[Ru(bpy)3]2+溶液光谱学性质的影响机制以及电解质效应. 相似文献
8.
Haruhiko Ikeda Takashi Monoi Yasuaki Sasaki 《Journal of polymer science. Part A, Polymer chemistry》2003,41(3):413-419
The catalysis of a silica‐supported chromium system {Cr[CH(SiMe3)2]3/SiO2} was compared with a silica‐supported chromium oxide catalyst, the Phillips catalyst (CrO3/SiO2). This catalyst was prepared by the calcining of the typical silica support used for the Phillips catalyst at 600 °C and by the support of tris[bis(trimethylsilyl)methyl]chromium(III) {Cr[CH(SiMe3)2]3} on the silica. In the slurry‐phase polymerization, this catalyst conducted the polymerization of ethylene at a high activity without organoaluminum compounds as cocatalysts or scavengers. The activity per Cr was about 6–7 times higher than that of the Phillips catalyst. Upon the introduction of hydrogen to the system, the molecular weight of polyethylene did not change with the Phillips catalyst, but it decreased with the Cr[CH(SiMe3)2]3/SiO2 catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 413–419, 2003 相似文献
9.
Vinyl polymerization of norbornene catalyzed by 2‐Py‐amidine Ni(II) complex/methylaluminoxane systems
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Yong‐Ping Niu Xiao‐Wei Wang Zhi‐Wu Zheng Xiao‐Fei Ma Jun‐Qing Cai Jun‐Kai Zhang Jin‐Lian Cheng 《应用有机金属化学》2014,28(9):688-695
Two 2‐Py‐amidine ligands (2‐Py―NH―C(Ph)═N―Ar, Ar = 2,6‐Me2C6H3 and 2,6‐iPr2C6H3) and the corresponding Ni(II) complexes ( 1 and 2 ) were synthesized and characterized using elemental analysis and FT‐IR, UV–visible, 1H NMR and 13C NMR spectroscopies. X‐ray crystal structures indicate that the chelate ring conformation of the less bulky complex 1 is relatively planar compared with that of the bulky complex 2 . Paramagnetic 1H NMR and 13C NMR studies show that, in solution, the time‐average structures of complexes 1 and 2 have mirror symmetry. Both complexes 1 and 2 were used as catalyst precursors for norbornene polymerization with methylaluminoxane as a co‐catalyst. The effects of Al/Ni ratio, temperature and structure of precursors on the catalytic performance were investigated. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
10.
Radical polymerization of acrylonitrile was carried out in an emulsifier-free condition initiated by KHSO5 catalyzed with Cu(II)/bis-salicylidene ethylene diamine (H2 Salen) complex. The Cu(II) salt alone, Cu(II)/salicylaldehyde and Cu(II)/ethylene diamine have a retarding effect on the polymerization reaction, while the chelate of Cu(II) with the tetradentate Schiff base ligand, H2 Salen has a catalytic effect. Prior to this, the catalytic effect of various bivalent transition metal salts and their couple with the Schiff base, H2 Salen on the polymerization reaction has been examined to be not significant. The in situ developed complex produces the stable emulsion leading to high conversion. In the polymerization, the variables studied were the concentration of monomer, initiator, Cu(II), H2 Salen and temperature. The overall activation energy was computed to be 13.1 kcal/mol. From the kinetic and spectral analyses, the mechanism of the initiator decomposition and initiation of polymerization by Cu(II)/H2 Salen complex were suggested. The rate of polymerization (Rp) was found to be dependent on the monomer, initiator, Cu(II) ion, H2 Salen concentrations to the 1.4, 0.3, 1.6, 1.5 power respectively. The polymers are characterized by IR and molecular weight by viscosity and GPC methods. 相似文献
11.
Parvaneh Shafieyoon Hosein Tavakol 《Phosphorus, sulfur, and silicon and the related elements》2018,193(5):324-328
The [N-(2-pyridyl)] para-styrene sulfonamide (PSS) was prepared as a monomer, from the reaction of para-styrene sulfonyl chloride and 2-amino pyridine in the presence of potassium hydroxide solution 0.5 M as a base, and CH3Cl. Polystyrene [N-(2-pyridyl) sulfonamide] (PPSS) was synthesized from the polymerization of [N-(2-pyridyl)] para-styrene sulfonamide (PSS). The Polystyrene bis [N-(2-pyridyl) sulfonamide] palladium (II) as a polymer- supporting palladium complex was also prepared from the reaction of PdCl2 (CH3CN)2 with PPSS in the presence of KOH 0.5 M. Polystyrene bis [N-(2-pyridyl) sulfonamide] palladium (II) is produced as a novel heterogeneous catalyst for coupling reactions for C-C bond formation. This method includes higher yield and has an easier work-up procedure. The structures of the monomer, polymer and its Pd complex were confirmed by using FT-IR and 1H-NMR spectroscopy. Elemental analysis of Pd by inductively coupled plasma (ICP) technique and hot filtration test showed loading of the metal into solution from the catalyst The heterogeneous catalyst was recycled without any loss in its properties. 相似文献
12.
Y. H. Huang W.-J. Wang S. Zhu G. L. Rempel 《Journal of polymer science. Part A, Polymer chemistry》1999,37(16):3385-3390
An on-line electron spin resonance (ESR) technique was applied to investigate the syndiospecific polymerization of styrene activated by the catalyst system CpTiCl3/MMAO. The measurements included trivalent titanocene concentration and monomer conversion. The activation procedure was found to have a dramatic effect on catalyst activity. Adding the reactants in the order of (MMAO + CpTiCl3) + St gave a much higher trivalent titanocene concentration and catalyst activity than the order of (MMAO + St) + CpTiCl3. The catalyst deactivation behaviors in the temperature range of 25–70°C were followed as a function of time during polymerization. At high Al/Ti ratios (500–1000), the decay rates of trivalent titanocene in the presence of styrene were much faster than those of the pure catalyst system. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3385–3390, 1999 相似文献
13.
Mangesh P. DushingC.V. Ramana 《Tetrahedron letters》2011,52(36):4627-4630
We report a simple strategy for the synthesis of a collection of C(3′)-spirodihydroisobenzo-furannulated nucleosides featuring a [2+2+2]-cyclotrimerization as the key reaction. The cyclotrimerization reactions are facile with the unprotected nucleosides having a diyne unit. When both alkynes of the diyne are terminal, the regioselectivity is poor. However, when one of the terminal alkynes is additionally substituted, the cyclotrimerizations are highly diastereoselective. Since the key bicycloannulation is the final step, this strategy provides flexibility in terms of the alkynes and is thus amenable for the synthesis of a focussed small molecule library. 相似文献
14.
Ceric ammonium nitrate (CAN) is found to be a suitable, inexpensive, and effective non-toxic catalyst for a smooth (3+2) cycloaddition of organic nitriles with NaN3 to afford 5-substituted 1H-tetrazoles in excellent yields. Shorter reaction times, easy work-up, and substantial and pure product formation are the key advantages of the present method. 相似文献
15.
To assess the compatibility of blends of synthetic poly(propylene carbonate) (PPC), with a natural bacterial poly(3-hydroxybutyrate) (PHB), a simple casting procedure of blend was used. poly(3-hydroxybutyrate)/poly(propylene carbonate) blends are found to be incompatible according to DSC and DMA analysis. In order to improve the compatibility and mechanical properties of PHB/PPC blends, poly(vinyl acetate) (PVAc) was added as a compatibilizer. The effects of PVAc on the thermal behavior, morphology, and mechanical properties of 70PHB/30PPC blend were investigated. The results show that the melting point and the crystallization temperature of PHB in blends decrease with the increase of PVAc content in blends, the loss factor changes from two separate peaks of 70PHB/30PPC blend to one peak of 70PHB/30PPC/12PVAc blend. It is also found that adding PVAc into 70PHB/30PPC blend can decrease the size of dispersed phase from morphology analysis. The result of tensile properties shows that PVAc can increase the tensile strength and Young’s modulus of 70PHB/30PPC blend, and both the elongation at break and the tensile toughness increase significantly with PVAc added into 70PHB/30PPC. 相似文献
16.
Pd(II) complexes bearing di‐ and monochelate fluorinated β‐ketonaphthyliminato ligand and their catalytic properties towards vinyl‐addition polymerization and copolymerization of norbornene and ester‐functionalized norbornene derivative
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Fluorinated β‐ketonaphthyliminate ligand CF3C(O)CHC[HN(naphthyl)]CH3 ( L1 ) and Pd(II) complexes with dichelate fluorinated β‐ketonaphthyliminato ligand, {CF3C(O)CHC[N(naphthyl)]CH3}2Pd ( C1 ), as well as with monochelate fluorinated β‐ketonaphthyliminato ligand, {CF3C(O)CHC[N(naphthyl)]CH3}Pd(CH3)(PPh3) ( C2 ), were synthesized and their solid‐state structures were confirmed using X‐ray crystallographic analysis. The Pd(II) complexes were employed as precursors to catalyze norbornene (NB) homo‐ and copolymerization with ester‐functionalized NB derivative using B(C6F5)3 as a co‐catalyst. High activity up to 2.3 × 105 gpolymer molPd?1 h?1 for the C1 /B(C6F5)3 system and 3.4 × 106 gpolymer molPd?1 h?1 for the C2 /B(C6F5)3 system was exhibited in NB homopolymerization. Moreover, the Pd(II) complexes exhibited a high level of tolerance towards the ester‐functionalized MB monomer. In comparison with the C1 /B(C6F5)3 system, the C2 /B(C6F5)3 system exhibited better catalytic property towards the copolymerization of NB with 5‐norbornene‐2‐carboxylic acid methyl ester (NB‐COOCH3), and soluble vinyl‐addition‐type copolymers were obtained with relatively high molecular weights (3.6 × 104–7.5 × 104 g mol?1) as well as narrow molecular weight distributions (1.49–2.15) depending on the variation of monomer feed ratios. The NB‐COOCH3 insertion ratio in all copolymers could be controlled in the range 2.8–21.0 mol% by tuning a content of 10–50 mol% NB‐COOCH3 in the monomer feed ratios. Copolymerization kinetics were expressed by the NB and NB‐COOCH3 monomer reactivity ratios: rNB‐COOCH3 = 0.18, rNB = 1.28 were determined for the C1 /B(C6F5)3 system and rNB‐COOCH3 = 0.19, rNB = 3.57 for the C2 /B(C6F5)3 system using the Kelen–Tüdõs method. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
17.
Kiyoshi Endo Tsuyoshi Nomaguchi Yoshikatsu Tsuchiya 《Journal of polymer science. Part A, Polymer chemistry》2007,45(17):3872-3876
Polymerization of vinyl chloride (VC) with titanium complexes containing Ti‐OPh bond in combination with methylaluminoxane (MAO) catalysts was investigated. Among the titanium complexes examined, Cp*Ti(OPh)3/MAO catalyst (Cp*; pentamethylcyclopentadienyl, Ph; C6H5) gave the highest activity for the polymerization of VC, but the polymerization rate was slow. From the kinetic study on the polymerization of VC with Cp*Ti(OPh)3/MAO catalyst, the relationship between the Mn of the polymer and the polymer yields gave a straight line, and the line passed through the origin. The Mw/Mn values of the polymer gradually decrease as a function of polymer yields, but the Mw/Mn values were somewhat broad. This may be explained by a slow initiation in the polymerization of VC with Cp*Ti(OPh)3/MAO catalyst. The results obtained in this study demonstrate that the molecular weight control of the polymers is possible in the polymerization of VC with the Cp*Ti(OPh)3/MAO catalyst. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3872–3876, 2007 相似文献
18.
Haiyang Gao Lixia Pei Yongfei Li Junkai Zhang Qing Wu 《Journal of molecular catalysis. A, Chemical》2008,280(1-2):81-86
Norbornene polymerizations with nickel complexes bearing [N,N] six-membered chelate ring activated with methylaluminoxane were investigated. The influence of ligand structure such as β-diimine, β-diketiminate, fluorinated β-diketiminate, and anilido-imine ligand on catalytic activities for norbornene polymerization was evaluated in detail. Ligands led to different electrophilicity of the nickel metal center, and a relatively positive nickel metal center would result in high catalytic activities for norbornene polymerization. The influences of polymerization temperature and Al/Ni ratio on norbornene polymerization with nickel catalysts bearing β-diimine, β-diketiminate, and fluorinated β-diketiminate ligands were also examined. All of the obtained polymers catalyzed by these nickel catalysts bearing [N,N] ligand are vinylic addition polynorbornenes with different molecular weights. 相似文献
19.
A novel method to prepare organic/inorganic composite particles, i.e. poly(methyl methacrylate)/CaCO3/SiO2
three-component composite particles, using emulsion polymerization of methyl methacrylate with sodium lauryl sulfate as a surfactant in an aqueous medium was reported. CaCO3/SiO2
two-component inorganic composite particles were obtained firstly by the reaction between Na2CO3 and CaCl2 in porous silica (submicrometer size) aqueous sol and the specific surface area of the particles was measured by the Brunauer–Emmett–Teller (BET) method. The results show that the BET specific surface area of the CaCO3/SiO2
composite particle is much smaller than that of the silica particle, indicating that CaCO3 particles were adsorbed by porous silica and that two-component inorganic composite particles were formed. Before copolymerization with methyl methacrylate, the inorganic composite particles were coated with a modifying agent through covalent attachment. The chemical structures of the poly(methyl methacrylate)/CaCO3/SiO2
composite particles obtained were characterized by Fourier transform IR spectroscopy and thermogravimetric analysis. The results show that the surface of the modified inorganic particles is grafted by the methyl methacrylate molecules and that the grafting percentage is about 15.2%. 相似文献
20.
Cigdem Yagci 《European Polymer Journal》2005,41(1):177-184
Redox initiated free-radical polymerization of methyl methacrylate (MMA) with allyl alcohol 1,2-butoxylate-block-ethoxylate (AABE) was carried out using cerium(IV) ammonium nitrate/nitric acid (HNO3) redox system to yield AABE-b-PMMA copolymers. The effects of MMA, AABE, Ce(IV) and HNO3 concentrations on the polymerization rate and polymer yield were investigated. The effect of temperature on the rate of polymerization and polymer yield was also investigated in the temperature range of 25-70 °C. Copolymers were characterized using GPC, FT-IR, 1H NMR and viscometry methods. 相似文献