Large ultra-high molecular weight polyethylene spherical particles produced by AlR3 activated half-sandwich chromium(III) catalysts

A series of half-sandwich pentamethylcyclopentadienyl chromium(III) complexes bearing a salicylaldiminato ligand, Cp*[2-R(1)-4-R(2)-6-(CH==NR(3))C(6)H(2)O]CrCl [R(1) = (i)Pr (1, 4), (t)Bu (2, 3, 5), Ad (6); R(2) = H (1, 2, 3), (t)Bu (4, 5, 6); R(3) = (i)Pr (1, 2, 5, 6), (t)Bu (3, 4)], were synthesized. All complexes were characterized by elemental analyses and the structures of complexes 1-4 and 6 were determined by X-ray diffraction analysis. These complexes adopt a pseudo-octahedral coordination environment with a three-legged piano stool geometry. Upon activation with a small amount of AlR(3), complexes 1-6 all catalyze the polymerization of ethylene in a quasi living fashion with good to high catalytic activity under mild conditions and produce ultra-high molecular weight polyethylene as spherical particles with a diameter of 1-6 mm. The catalytic activity of these complexes and the molecular weight of the produced polyethylene can be tuned in a broad range by changing the R(1), R(2), and R(3) groups as well as the AlR(3) cocatalyst. It was found that complex 6 with R(1) = Ad, R(2) = (t)Bu, and R(3) = (i)Pr shows the highest catalytic activity and produces polyethylene with the highest molecular weight.     

聚(酰胺-胺)树状大分子负载钛催化乙烯聚合

用水杨醛对第一代聚(酰胺-胺)(PAMAM)树状大分子通过Schiff碱缩合反应进行修饰,然后再与TiCl4.2THF反应,得到了树状大分子负载的钛配合物,并用1H-NMR、电感耦合等离子体发射光谱法(ICP-AES)和电喷雾电离质谱法(ESI-MS)对其结构进行了表征.用甲基铝氧烷(MAO)活化,将其用作乙烯聚合的催化剂前体.当Al/Ti比为1000时,可得良好的活性.聚乙烯的粘弹性能表明材料为超高分子量的聚乙烯.     

水杨醛亚胺镍配合物催化的乙烯水相聚合

在含表面活性剂的水相体系中, 用一系列水杨醛亚胺镍配合物催化乙烯聚合, 得到了高分子量低支化度聚乙烯. 研究表明水杨醛亚胺镍配合物中苯环上取代基的电子效应和空间位阻对乙烯聚合活性和聚合物的分子量有所影响. 提高配合物酚氧环上取代基的吸电子性, 聚合活性相应增加, 但聚乙烯的分子量降低; 而增加苯胺环上取代基的空间位阻, 聚合活性和聚乙烯的分子量均增加. 粘度法测得由水相聚合得到的聚乙烯的分子量在10⁴～10⁵范围内. DSC测得该聚乙烯的结晶度在50%～70%之间, 熔点在115～137 ℃范围内. GPC分析表明用环辛二烯合镍[Ni(COD)₂]助催化乙烯, 聚乙烯的分子量分布随酚氧环上取代基电负性增加而从双峰到单峰变化, 动态流变学研究进一步说明了聚乙烯分子量及其分布的变化.     

Half-zirconocene anilide complexes: synthesis, characterization and catalytic properties for ethylene polymerization and copolymerization with 1-hexene

A number of half-zirconocene anilide complexes of the type Cp*ZrCl(2)[N(2,6-R(1)(2)C(6)H(3))R(2)] [R(1) = (i)Pr (1, 3), Me (2); R(2) = Me (1, 2), Bn (3)] and Cp*ZrCl[N(2,6-Me(2)C(6)H(3))Me](2) (4) (Cp* = pentamethylcyclopentadienyl) were synthesized from the reactions of Cp*ZrCl(3) with the lithium salts of the corresponding anilide in diethyl ether at room temperature. All new zirconium complexes were characterized by (1)H and (13)C NMR and elemental analysis. Molecular structures of complexes 1, 2 and 4 were determined by single crystal X-ray diffraction analysis. Upon activation with Al(i)Bu(3) and Ph(3)CB(C(6)F(5))(4), complexes 1-4 exhibit good catalytic activity for ethylene polymerization, and produce polyethylene with a moderate molecular weight. Among these zirconium complexes, complex 1 shows the highest catalytic activity while complex 4 shows the lowest catalytic activity for ethylene polymerization. Complexes 1-3 also exhibit moderate catalytic activity for copolymerization of ethylene with 1-hexene, and produce copolymers with relatively high molecular weight and reasonable 1-hexene incorporation. In addition, the activation procedure of these catalyst systems were studied by (1)H NMR spectroscopy.     

Water-soluble salicylaldiminato Ni(II)-methyl complexes: enhanced dissociative activation for ethylene polymerization with unprecedented nanoparticle formation

Water-soluble single-component (kappa2-N,O)-salicylaldiminato nickel-methyl complexes 1-4-L (L = TPPTS, TPPDS, H2N-PEG-OMe) allow for the catalytic polymerization of ethylene under organic solvent-free aqueous conditions producing high molecular weight polyethylene with particle sizes below 10 nm. Amphiphilic TPPDS- and H2N-PEG-OMe complexes exhibit a polymerization activity in water higher than that in toluene. A solvation-favored activation of precatalysts 1-4-L by equilibrium dissociation of L in aqueous solution likely accounts for this enhanced polymerization activity. The observed generation of a given particle by a single active site is an unprecedented mechanism for formation of aqueous particle dispersions.     

Synthesis of bimodal molecular weight distribution polyethylene with α-diimine nickel(II) complexes containing unsym-substituted aryl groups in the presence of methylaluminoxane

A series of unsymmetrical complexes of 2,3-bis(2-phenylphenyl)-butanediimine nickel(II) dibromide (complex 1), 1,4-bis(2-isopropyl-6-methylphenyl)-acenaphthenediimine nickel(II) dibromide (complex 2) and meso- and rac-1,4-bis (2,4-di-tert-butyl-6-methylphenyl)-acenaphthenediimine nickel(II) dibromide (meso-3 and rac-3) were synthesized and activated by methylaluminoxane (MAO) for ethylene polymerization. By ¹³C NMR characterization, meso- and rac-stereo-isomers were detected in the condensation products resulting from the reaction of unsym-substituted anilines with diketones. It was notable that meso- and rac-isomers in ligand 1 or ligand 2 could not be separated owing to their interconversion, however, meso- and rac-isomers in ligand 3 could be isolated and identified by X-ray diffraction and NMR analysis. At low polymerization temperatures, complex 1/MAO afforded polyethylene with bimodal molecular weight distribution, while complex 2/MAO prepared polyethylene with single-modal distribution. Moreover, by raising polymerization temperature or extending time of catalyst aging, bimodal molecular weight distribution polyethylene was also produced by complex 2/MAO. The hypothesis of bimodal molecular weight distribution polyethylene synthesized by unsymmetrical α-diimine nickel(II) complexes was supported that the molecular weight of polyethylene produced by rac-3/MAO was significantly higher than that produced by meso-3/MAO under identical polymerization conditions. A unique methodology to prepare polyethylene with bimodal molecular weight distribution was demonstrated.     

铁系后过渡金属催化剂/不同铝氧烷体系制备具有双峰分子量分布的聚乙烯

分子量及其分布对聚烯烃的机械性能和流变性能影响显著．高分子量聚烯烃机械性能好,但加工性能差;低分子量聚烯烃则恰恰相反,机械性能较差,但加工性能好．宽峰或双峰分子量分布聚烯烃同时具有高、低分子量聚烯烃的优点,受到人们的普遍重视．目前,制备宽峰及双峰分子量聚烯烃主要采用物理共混、     

Immobilization and activation of 2,6-bis(imino)pyridyl Fe, Cr and V precatalysts using a MgCl2/AlRn(OEt)3−n support: Effects on polyethylene molecular weight and molecular weight distribution

Ethylene polymerizations carried out with various bis(imino)pyridyl iron, chromium and vanadium complexes immobilized on a MgCl₂/AlR_n(OEt)_3−n support gave relatively broad polyethylene molecular weight distributions in the case of iron, but high molecular weight and a very narrow molecular weight distribution with vanadium, indicative of a single active species. The narrow MWD was confirmed by melt rheometry. Similar results were obtained after reaction of the bis(imino)pyridyl complex LVCl₃ (6) with MeLi or AlEt₃, where alkylation of the pyridine ring gives a complex L′VCl₂ (7). In the case of chromium, a bimodal distribution was obtained, with evidence of incomplete catalyst immobilization. The polyethylene molecular weights obtained with the iron complexes were strongly dependent on the substituents in the bis(imino)pyridyl ligand, and were somewhat higher than have been obtained in homogeneous polymerization. In contrast, the molecular weights obtained with the bis(imino)pyridyl chromium and vanadium complexes were much higher that those previously obtained under homogeneous conditions. In all cases, the activities of the immobilized catalysts were higher than those found in homogeneous polymerization.     

配体骨架烷基取代基对α-二亚胺镍催化乙烯聚合的影响

合成了4种α-二亚胺镍催化剂Ar—NC(R1)C(R2)N—ArNiBr2[Ar=2,6-dimethylphenyl,R1=CnH2n+1,R2=CmH2m+1;其中Cat1:m=1,n=1;Cat2:m=2,n=1;Cat3:m=3,n=1;Cat4:m=2,n=2],考察了聚合温度、催化剂浓度和催化剂配体骨架碳原子上烷基取代基对乙烯聚合反应活性、聚合物链结构和结晶性能的影响.实验发现,当配体骨架上烷基取代基R1和R2不同时,催化剂具有较高的活性,且聚合物分子量也较高;其中,Cat2和Cat3在20℃,乙烯常压和5.8mmol/L催化剂用量下,乙烯聚合活性达1.86×103kgPE/(molNi.h)和1.92×103kgPE/(molNi.h),聚合物分子量(Mw)达6.82×105和1.019×105.聚乙烯链结构分析表明,甲基支链在聚乙烯支链中占主导地位,支化度主要受反应温度的影响;同时还发现,配体骨架碳原子上烷基取代基不同的二亚胺镍催化合成聚乙烯的长支链比例相对较高,特别是在较高反应温度40℃下,己基及以上长支链比例明显增加.     

Titanium isopropoxide complexes of a series of sterically demanding aryloxo based [N2O2]2- ligands as precatalysts for ethylene polymerization

Several titanium isopropoxide complexes [N,N'-bis(2-oxo-3-R(1)-5-R(2)-phenylmethyl)-N,N'-bis(methylene-p-R(3)-C(6)H(4))-ethylenediamine]Ti(O(i)Pr)(2) [R(1) = t-Bu, R(2) = Me, R(3) = H (1b); R(1) = R(2) = t-Bu, R(3) = H, (2b); R(1) = R(2) = Cl, R(3) = H, (3b), R(1) = t-Bu, R(2) = Me, R(3) = Cl (4b); R(1) = R(2) = t-Bu, R(3) = Cl, (5b); R(1) = R(2) = R(3) = Cl, (6b)] supported over sterically demanding aryloxy based [N(2)O(2)]H(2) ligands have been designed as precatalysts for the ethylene polymerization. Specifically, the 1b-6b complexes, when treated with methylaluminoxane (MAO) under 88 ± 0.5 psi of ethylene at 30 °C for 3 h, produced polyethylene polymers of high molecular weight (M(w) = ca. 7.2-8.3 × 10(5) g mol(-1)) having broad molecular weight distribution (PDI = ca. 13.1-14.6). The 1b-6b complexes were conveniently synthesized from the direct reaction of the [N(2)O(2)]H(2) ligands, 1a-6a, with Ti(O(i)Pr)(4) in 69-86% yield.     

Enhancing performance of α-diiminonickel precatalyst for ethylene polymerization by substitution with the 2,4-bis(4,4'-dimethoxybenzhydryl)-6-methylphenyl group

High activities in ethylene polymerization predetermine α-diiminonickel precatalysts for potential industrial applications. In our study, we have synthesized and characterized a series of unsymmetrical 1-(2,4-bis(4,4′-dimethoxybenzhydryl)-6-MeC₆H₂N)-2-arylimino-acenaphthylene nickel(II) halides. The single-crystal X-ray diffraction study of representative compounds reveals distorted tetrahedral geometry. On activation with either Me₂AlCl or modified methylaluminoxane, these nickel complexes exhibit high activities of the order of 10⁶ g of PE (mol of Ni)⁻¹ h⁻¹ and produce polyethylene of generic application characterized by high molecular weight, narrow molecular weight distribution, and moderate degree of branching. The substituents at the ligands affect the catalytic performance of the nickel complexes and tune the microstructure of the resultant polyethylene.     

三种不同碳桥联双核茂钛配合物的合成及催化乙烯聚合研究

合成了3种不同结构的CnH₂n桥联双核茂钛配合物(CH₃)₂C[(C₅H₄)TiCl₂(C₅H₅)]₂(3),(CH₂)_n[(C₅H₄)TiCl₂(C₅H₅)]₂(6,n=3;7,n=4),并用1HNMR进行了表征.发现以甲苯为溶剂时,不仅提高了产率,而且有效地避免了副产物Cp₂TiCl₂的生成.研究了化合物7/MAO(甲基铝氧烷)催化乙烯聚合的反应,考察了反应条件对催化体系的影响.结果表明,催化活性随着n(Al)/n(Cat.)比的增大而提高,聚乙烯的分子量在n(Al)/n(Cat.)=500和50℃时达到最高值9.0102×10⁴;随着聚合时间的延长,催化活性下降,而产物分子量不断升高;随着温度的上升,50℃时催化活性和聚乙烯的分子量最高,分别为2.4074×10⁵gPE/(molTi·h)和6.8679×10⁴.随着桥联双核茂钛配合物碳桥的增长,催化活性增加,所得聚乙烯的分子量降低.     

Synthesis of hydroxy-functionalized ultrahigh molecular weight polyethylene using fluorenylamidotitanium complex

Copolymerizations of ethylene and 1-dodecene were conducted with a series of ansa-fluorenylamidodimethyltitanium complexes, [t-BuNSiMe_2Flu]TiMe_2(1a), [t-BuNSiMe_2(2,7-~tBu_2Flu)]TiMe_2(1 b), and [(1-adamantyl)NSiMe_2(2,7-~tBu_2Flu)]TiMe_2(1c) activated by modified methylaluminoxane. The activity increased by the introduction of the alkyl groups on the fluorenyl and amido ligands, and 1c produced the highest molecular weight copolymers. Complex 1c also promoted copolymerization of ethylene and ~iBu_3 Al protected 10-undecen-1-ol with high activity(~2000 kg·mol~(-1)·h~(-1)), affording hydroxy-functionalized ultrahigh molecular weight polyethylene. The hydroxy content of the copolymers obtained was controllable by changing comonomer feed ratio. The introduction of a small amount of hydroxy group can alter the surface properties of polyethylene.     

Synthesis of polyethylene with bimodal molecular weight distribution by supported iron‐based catalyst

Through immobilization of two iron‐based complexes, [((2,6‐MePh)N = C(Me))₂C₅H₃N]FeCl₂ ( 1 ) and [((2,6‐iPrPh)N = C(Me))₂C₅H₃N]FeCl₂ ( 2 ), on SiO₂ pretreated with tetraethylaluminoxane (TEAO), two supported iron‐based catalysts, 1 /TEAO/SiO₂ ( 3 ) and 2 /TEAO/SiO₂ ( 4 ), were prepared. These two supported catalysts 3 and 4 could be used to catalyze ethylene polymerization with moderate polymerization activity and prepare linear high‐density polyethylene with bimodal molecular weight distribution (MWD). It was demonstrated that immobilization of catalyst could significantly improve molecular weight (MW) of high‐MW fraction of the resultant polyethylene, as well as maintain bimodal MWD of polyethylene produced by the corresponding homogeneous catalysts. Such bimodal MWD of polyethylene produced by supported iron‐based catalysts could be well tailored by varying polymerization conditions, such as ethylene pressure and molar ratio of Al to Fe. It has been proven that TEAO is an efficient activator for both homogeneous and heterogeneous iron‐based catalysts for producing polyethylene with bimodal MWD. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5662–5669, 2004     

Highly Robust Palladium(II) α‐Diimine Catalysts for Slow‐Chain‐Walking Polymerization of Ethylene and Copolymerization with Methyl Acrylate

A series of sterically demanding α‐diimine ligands bearing electron‐donating and electron‐withdrawing substituents were synthesized by an improved synthetic procedure in high yield. Subsequently, the corresponding Pd complexes were prepared and isolated by column chromatography. These Pd complexes demonstrated unique properties in ethylene polymerization, including high thermal stability and high activity, thus generating polyethylene with a high molecular weight and very low branching density. Similar properties were observed for ethylene/methyl acrylate copolymerization. Because of the high molecular weight and low branching density, the generated polyethylene and ethylene/methyl acrylate copolymer were semicrystalline solids. The (co)polymers had unique microstructures originating from the unique slow‐chain‐walking activity of these Pd complexes.     

MgCl_2负载双金属复合催化剂制备宽分子量分布聚乙烯

聚乙烯的分子量和分子量分布对其熔体的流变性能和产品的力学性能有显著影响．分子量分布的变化,尤其是分子量分布末端部位的变化,都会对材料的注塑行为产生大的影响［１］．为了控制Ｚｉｅｇｌｅｒ催化剂制备的聚乙烯分子量分布而改善聚合工艺的报道很多［２～４］,工业生产中可利用多步聚合工艺来获得宽分子量分布的聚乙烯［５,６］,但这种方法工艺复杂,成本高．美国ＵＣＣ公司利用复合的ＴｉＶ和ＺｒＶ催化剂在气相法Ｕｎｉｐｏｌ工艺装置上首次成功的合成出了双峰高分子量聚乙烯产品［７,８］,由于采用Ｕｎｉｐｏｌ生产工艺…     

α-二亚胺镍/Cp*TiCl3复式催化剂制备双峰长支链聚乙烯

合成了一种后过渡金属镍化合物 [二 N ,N′ (α 萘基 ) 2 ,3 丁二亚胺镍二溴化物 ][C1 0 H7—NC(CH3)C(CH3)N—C1 0 H7]NiBr2 ,此化合物在MAO活化下催化乙烯聚合能得到含有末端双键的低分子量聚乙烯 ,即长链α 烯烃 .此化合物和一种单茂钛化合物五甲基环戊二烯基三氯化钛 (Cp TiCl3)所组成的复式催化剂 ,用MAO活化后两种主催化剂具有良好协同作用 ,能使单一乙烯聚合制备出双峰型长支链的聚乙烯 .1 3C NMR表明由此复式催化剂制得的聚乙烯不但含有甲基、乙基、丙基、丁基、戊基支链而且还含有相当多的长支链 (支链长度大于或等于 6 ) .催化剂的摩尔比 (Ni Ti)、Al(MAO) (Ni+Ti)摩尔比和聚合温度等聚合条件对催化活性及聚合物的结构与性能有明显影响 .GPC测试表明所得到的支化聚乙烯分子量呈双峰分布 .     

N-(5,6,7-trihydroquinolin-8-ylidene)-2-benzhydrylbenzenaminonickel halide complexes: synthesis, characterization and catalytic behavior towards ethylene polymerization

A series of N-(5,6,7-trihydroquinolinylidene)-2-benzhydrylbenzenamine ligands was synthesized and characterized by (1)H/(13)C NMR and IR spectroscopy, and by elemental analysis. These ligands reacted with NiCl(2) or NiBr(2)(DME) to form the title halide complexes, which were also characterized by IR spectroscopy and elemental analysis. Single crystal X-ray diffraction revealed that the representative nickel complexes crystallized as centro-symmetric dimers with chloro-bridges linking distorted octahedral nickel centers. On activation with either methylaluminoxane (MAO) or diethylaluminium chloride (Et(2)AlCl), all nickel pre-catalysts showed high activities for ethylene polymerization, producing polyethylene with narrow molecular weight distribution, consistent with single-site catalysis. The nature of the ligands and reaction parameters were investigated and discussed in terms of their influence on the catalytic behavior of these nickel pre-catalysts.     

Synthesis, characterization, and catalytic properties of new half-sandwich zirconium(IV) complexes

A number of new half-sandwich zirconium(IV) complexes bearing N,N-dimethylaniline-amido ligands with the general formula Cp*ZrCl(2)[ortho-(RNCH(2))(Me(2)N)C(6)H(4)] [R = 2,6-Me(2)C(6)H(3) (1), 2,6-(i)Pr(2)C(6)H(3) (2), (i)Pr (3), (t)Bu (4)] were synthesized by the reaction of Cp*ZrCl(3) with the corresponding ortho-(Me(2)N)C(6)H(4)CH(2)NRLi. All new zirconium complexes were characterized by (1)H and (13)C NMR, elemental analyses and single crystal X-ray diffraction analysis. The molecular structural analysis reveals that the NMe(2) group does not coordinate to the zirconium atom in all cases. Complexes 1-4 all have a pseudo-tetrahedral coordination environment in their solid state structures and adopt a three-legged piano stool geometry for the zirconium atoms with the amide N atom and the two Cl atoms being the three legs and the Cp* ring being the seat. Variable-temperature (1)H NMR experiments for all complexes 1-4 were performed to investigate the possible intramolecular interaction between the N atom in the NMe(2) group and the central zirconium atom in solution. Upon activation with Al(i)Bu(3) and Ph(3)CB(C(6)F(5))(4), complexes 1-4 all exhibit moderate to good catalytic activity for ethylene polymerization and copolymerization with 1-hexene, producing linear polyethylene or poly(ethylene-co-1-hexene) with moderate molecular weight and reasonable 1-hexene incorporation.     

Binuclear half-metallocene chromium(III) complexes mediated ethylene polymerization with alkylaluminium as cocatalyst

Binuclear half-metallocene chromium complexes {Cp*[3-(CH==NR)-2-O-C(10)H(5)]CrCl}(2) [Cp* = C(5)Me(5); R = (i)Pr (1), Ph (2), 2,6-(i)Pr(2)C(6)H(3) (3)] based on 1,1'-binaphthyl ligands, as well as their mononuclear analogues Cp*[3-(CH==NR)-2'-R'-2-O-C(20)H(11)]CrCl [R = (i)Pr, R' = (n)BuO (4), R = Ph, R' = (n)BuO (5), R = 2,6-(i)Pr(2)C(6)H(3), R' = (n)BuO (6), R = (i)Pr, R' = H (7)], were synthesized and characterized by mass spectrometry, elemental analysis, magnetic measurement, and UV-vis spectroscopy. The molecular structures of complexes 1, 3, 5 and 6 were further confirmed by single-crystal X-ray crystallographic analysis. When activated with a small amount of AlMe(3), these binuclear complexes exhibited higher activities in catalyzing ethylene polymerization in comparison with their mononuclear analogues, affording high molecular weight polymers with unimodal molecular weight distributions. The highest activity up to 2.87 × 10(6) g PE (mol Cr)(-1) h(-1) was achieved in the catalyst system of complex 3 bearing a bulky 2,6-(i)Pr(2)C(6)H(3) group on the imine nitrogen atom in the presence of 25 equiv. AlMe(3) as activator at 20 °C. (13)C NMR analysis indicates the resultant polymers are linear and no evidence on branch was found.