半茂钛催化乙烯与降冰片烯共聚的理论研究

运用密度泛函方法对含酚-膦配体的半茂钛化合物催化乙烯与降冰片烯共聚合反应的详细机理进行了理论研究.计算结果表明,虽然由于配体的不同,此系列钛化合物具有两种典型结构,但其在助催化剂作用下形成的催化活性种均为相似的P-Ti成键的阳离子物种.在烯烃聚合反应中,烯烃单体的配位插入反应易于从阳离子活性种中氧原子的对位发生.由乙烯及降冰片烯聚合反应各步骤的比较可知,乙烯单体插入Ti-Me结构的初始插入步骤较插入Ti-Et结构困难得多,因而链引发步骤为乙烯均聚的决速步骤.而降冰片烯单体插入Ti-Me结构较之乙烯单体容易得多,但由于降冰片烯单体位阻较大,其连续插入十分困难.在共聚反应过程中,NBE单体的引入可以使得Et插入反应容易越过较难的插入Ti-Me结构步骤,这是NBE与Et共聚反应的反应活性远大于催化Et均聚反应的最主要原因.     

邻-酚羟基取代N-杂环卡宾[C,O]螯合双配体镍/MAO催化降冰片烯加成聚合的研究

3种邻-酚羟基取代的N-杂环卡宾[C,O]螯合双配体镍配合物在甲苯中以甲基铝氧烷(MAO)为助催化剂,催化降冰片烯(NBE)聚合.考察了反应温度、时间、n(Al)/n(Ni)以及n(NBE)/n(Ni)等因素对催化活性和所得聚降冰片烯相对分子质量及其分布的影响.结果表明,0℃时催化体系的聚合活性可达,1.34×107gPNBE/(molNi.h);所得聚降冰片烯(PNBE)重均相对分子质量(Mw)可达2.0×106,相对分子质量分布(Mw/Mn)为3.3~1.5,热分解温度在440℃附近,且在室温下可溶于环己烷和三氯苯.通过对聚合产物FTIR,13C-NMR和WAXD分析表明,该聚合反应以烯烃加成聚合方式进行,且聚合物是非晶态结构.     

降冰片烯开环易位聚合反应的分子量及分子量分布控制

使用Grubbs催化剂催化降冰片烯单体进行开环易位聚合反应, 研究了催化剂搅拌溶解时间、聚合反应的溶剂极性和三苯基膦的加入等反应条件对降冰片烯单体ROMP反应分子量及分子量分布的影响, 从而得到降冰片烯ROMP反应的最佳条件.     

Fe(acac)3-Al(i-Bu)3-CCl4催化马来酸酐与降冰片烯共聚

 研究了Fe(acac)3-Al(i-Bu)3-CCl4(acac=乙酰丙酮)催化体系对马来酸酐(MA)与降冰片烯(NBE)交替聚合反应的催化性能. 用元素分析、核磁共振和红外光谱研究了共聚物的结构,在单体比为1∶1时,共聚物中MA和NBE的含量分别为52.2%和47.8%. 凝胶渗透色谱结果表明共聚物分子量分布窄. 动力学研究结果表明, MA与NBE共聚对单体浓度呈一级反应,其表观活化能为74.3 kJ/mol.     

双吡唑亚胺镍/甲基铝氧烷催化降冰片烯的聚合

合成了两种双吡唑亚胺镍配合物: 双-N-(苯基-1-3,5-二甲基吡唑基亚甲基)苯基亚胺二溴化镍(Cat.1)和双-4-甲氧基-N-(苯基-1-3,5-二甲基吡唑基亚甲基)苯基亚胺二溴化镍(Cat.2). 研究了Cat.1/MAO和Cat.2/MAO催化体系对降冰片烯(NBE)单体聚合的催化性能, 考察了各种聚合条件, 如温度、Al/Ni摩尔比及催化剂浓度对降冰片烯的催化效率、单体转化率、聚合物分子量及分子量分布的影响. 研究结果表明, Cat.1/MAO和Cat.2/MAO催化体系对降冰片烯聚合具有较高的催化效率, 可达到105 g PNBE/(mol Ni)数量级, 所得聚降冰片烯(PNBE)的重均分子量在105以上, 分子量分布指数在2左右. 聚合产物的1H NMR和FTIR谱分析结果表明, 该聚合反应是以单体的乙烯基加成聚合机理进行的.     

氮配位单茂金属烯烃聚合催化剂

本文综述了近些年来以含氮基团为阴离子配体的单茂金属化合物作为烯烃精确聚合的催化剂的研究。氮配位单茂金属催化剂在烯烃聚合中显示出独特的特性,特别是对于乙烯的共聚合,不仅能得到Ziegler-Natta催化剂和传统茂金属催化剂不能合成的新的共聚物,还有优于其他单茂金属催化剂的共聚活性。环戊二烯基和含氮阴离子配体的改性是所得催化剂聚合效果的关键。本文涉及了乙烯均聚以及乙烯与α-烯烃(己烯-1、辛烯-1等)、苯乙烯和环烯烃(降冰片烯、四环十二碳烯等)的共聚合。     

氯乙酸降冰片烯甲酯制备方法的改进

在环烯烃开环歧化聚合反应(ROMP)中,降冰片烯类是一类应用的最多的单体。为合成具有高反应活性的单体,选择双环戊二烯与烯丙醇隔绝空气下的Diels-Alder反应,产物与α-氯代乙酰氯反应得到氯乙酸降冰片烯甲酯,在实验中对反应的温度、时间、比例等条件进行进一步精确。     

四氯化钛/三异丁基铝体系催化降冰片烯与异戊二烯的共聚合

以传统Ziegler-Natta催化体系TiCl4/Al(#em/em#-Bu)3催化降冰片烯(NBE)和异戊二烯(IP)的共聚合, 制得可溶于常规有机溶剂的共聚物, 其数均分子量为2.0 × 104~6.5 × 104, 分子量分布指数为1.5~2.9, 降冰片烯结构摩尔含量为26%~60%. 考察了助催化剂用量、 聚合温度及2种单体投料比对共聚合的影响. 结果表明, 当降冰片烯与异戊二烯的投料摩尔比为4∶6时, 于40 ℃聚合6 h, 得到的共聚物产率为96%, 数均分子量为6.5×104, 降冰片烯结构含量45%. 用 1H NMR, 13CNMR, GPC和DSC等方法表征了共聚产物的微观结构与热性能. 13C NMR DEPT结果表明, 共聚反应中降冰片烯单体以加成方式聚合. DSC结果显示, 共聚物只有一个玻璃化转变温度(Tg=20~40 ℃). 通过Kelen-Tüdös方法得到2种单体的竞聚率分别为rNBE=0.07, rIP=0.44.     

锆茂均相催化体系催化乙烯与降冰片烯共聚合的研究

锆茂均相催化体系催化乙烯与降冰片烯共聚合的研究谢光华，王金梅，张盛庆（中国科学院化学研究所，北京，１０００８０）关键词锆茂均相催化体系，乙烯，降冰片烯，共聚合金属二茂基化合物与甲基铝氧烷（ＭｅｔｈｙｌａｌｕｎｕｎｏｘａｎｅＭＡＯ）组成以甲苯为溶剂的均...     

载体化络合催化开环歧化聚合合成梳形接枝共聚物研究

由环戊二烯（CPD）及烯丙基氯（AC）经聚合物支载三氟化硼催化的Diels-Alder反应合成了5-氯甲基-2-降冰片烯（NB-CH2Cl),锂代后用以引发甲基丙烯酸甲酯（MMA）及苯乙烯（S）的活性阴离子聚合,合成了带聚合物取代基的降冰片烯大分子单体NB-PMMA及NB-PS。在聚合物支载钌卡宾络合物催化作用下进行所合成大分子单体的开环歧化聚合反应（ROMP）,合成了二种接枝于开环歧化聚降冰片烯（PNB）主链的梳形接技共聚物PNB-g-PMMA及PNB-g-PS。实验结果表明所研制聚合物支载硼、钌络合物催化性能明显优于对应非支载活性种。     

Redox‐Controlled Olefin (Co)Polymerization Catalyzed by Ferrocene‐Bridged Phosphine‐Sulfonate Palladium Complexes

The facile and reversible interconversion between neutral and oxidized forms of palladium complexes containing ferrocene‐bridged phosphine sulfonate ligands was demonstrated. The activity of these palladium complexes could be controlled using redox reagents during ethylene homopolymerization, ethylene/methyl acrylate copolymerization, and norbornene oligomerization. Specifically in norbornene oligomerization, the neutral complexes were not active at all whereas the oxidized counterparts showed appreciable activity. In situ switching between the neutral and oxidized forms resulted in an interesting “off” and “on” behavior in norbornene oligomerization. This work provides a new strategy to control the olefin polymerization process.     

Kinetics and mechanism of metallocene‐catalyzed olefin polymerization: Comparison of ethylene,propylene homopolymerizations,and their copolymerization

A series of ethylene, propylene homopolymerizations, and ethylene/propylene copolymerization catalyzed with rac‐Et(Ind)₂ZrCl₂/modified methylaluminoxane (MMAO) were conducted under the same conditions for different duration ranging from 2.5 to 30 min, and quenched with 2‐thiophenecarbonyl chloride to label a 2‐thiophenecarbonyl on each propagation chain end. The change of active center ratio ([C^*]/[Zr]) with polymerization time in each polymerization system was determined. Changes of polymerization rate, molecular weight, isotacticity (for propylene homopolymerization) and copolymer composition with time were also studied. [C^*]/[Zr] strongly depended on type of monomer, with the propylene homopolymerization system presented much lower [C^*]/[Zr] (ca. 25%) than the ethylene homopolymerization and ethylene–propylene copolymerization systems. In the copolymerization system, [C^*]/[Zr] increased continuously in the reaction process until a maximum value of 98.7% was reached, which was much higher than the maximum [C^*]/[Zr] of ethylene homopolymerization (ca. 70%). The chain propagation rate constant (k_p) of propylene polymerization is very close to that of ethylene polymerization, but the propylene insertion rate constant is much smaller than the ethylene insertion rate constant in the copolymerization system, meaning that the active centers in the homopolymerization system are different from those in the copolymerization system. Ethylene insertion rate constant in the copolymerization system was much higher than that in the ethylene homopolymerization in the first 10 min of reaction. A mechanistic model was proposed to explain the observed activation of ethylene polymerization by propylene addition. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 867–875     

Living copolymerization of ethylene with norbornene catalyzed by bis(pyrrolide-imine) titanium complexes with MAO

Bis(pyrrolide-imine) Ti complexes in conjunction with methylalumoxane (MAO) were found to work as efficient catalysts for the copolymerization of ethylene and norbornene to afford unique copolymers via an addition-type polymerization mechanism. The catalysts exhibited very high norbornene incorporation, superior to that obtained with Me(2)Si(Me(4)Cp)(N-tert-Bu)TiCl(2) (CGC). The sterically open and highly electrophilic nature of the catalysts is probably responsible for the excellent norbornene incorporation. The catalysts displayed a marked tendency to produce alternating copolymers, which have stereoirregular structures despite the C(2) symmetric nature of the catalysts. The norbornene/ethylene molar ratio in the polymerization medium had a profound influence on the molecular weight distribution of the resulting copolymer. At norbornene/ethylene ratios larger than ca. 1, the catalysts mediated room-temperature living copolymerization of ethylene and norbornene to form high molecular weight monodisperse copolymers (M(n) > 500,000, M(w)/M(n) < 1.20). (13)C NMR spectroscopic analysis of a copolymer, produced under conditions that gave low molecular weight, demonstrated that the copolymerization is initiated by norbornene insertion and that the catalyst mostly exists as a norbornene-last-inserted species under living conditions. Polymerization behavior coupled with DFT calculations suggested that the highly controlled living polymerization stems from the fact that the catalysts possess high affinity and high incorporation ability for norbornene as well as the characteristics of a living ethylene polymerization though under limited conditions (M(n) 225,000, M(w)/M(n) 1.15, 10-s polymerization, 25 degrees C). With the catalyst, unique block copolymers [i.e., poly(ethylene-co-norbornene)(1)-b-poly(ethylene-co-norbornene)(2), PE-b-poly(ethylene-co-norbornene)] were successfully synthesized from ethylene and norbornene. Transmission electron microscopy (TEM) indicated that the PE-b-poly(ethylene-co-norbornene) possesses high potential as a new material consisting of crystalline and amorphous segments which are chemically linked.     

Vinyl addition polymerization of norbornene with cationic (allyl)Ni catalysts: Mechanistic insights and characterization of first insertion products

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     

Notable norbornene (NBE) incorporation in ethylene-NBE copolymerization catalysed by nonbridged half-titanocenes: better correlation between NBE incorporation and coordination energy

CpTiCl2(N=CtBu2) exhibits both remarkable catalytic activity and efficient norbornene (NBE) incorporation for ethylene-NBE copolymerization: the NBE incorporation by Cp'TiCl2(X) (X = N=CtBu2, O-2,6-iPr2C6H3; Cp' = Cp, C5Me5, indenyl) was related to the calculated coordination energy after ethylene insertion.     

Homo‐ and copolymerization of ethylene and norbornene with bis(β‐diketiminato) titanium complexes activated with methylaluminoxane

Homo‐ and copolymerization of ethylene and norbornene were investigated with bis(β‐diketiminato) titanium complexes [ArNC(CR₃)CHC(CR₃)NAr]₂TiCl₂ (R = F, Ar = 2,6‐diisopropylphenyl 2a; R = F, Ar = 2,6‐dimethylphenyl 2b ; R = H, Ar = 2,6‐diisopropylphenyl 2c ; R = H, Ar = 2,6‐dimethylphenyl 2d) in the presence of methylaluminoxane (MAO). The influence of steric and electric effects of complexes on catalytic activity was evaluated. With MAO as cocatalyst, complexes 2a–d are moderately active catalysts for ethylene polymerization producing high‐molecular weight polyethylenes bearing linear structures, but low active catalysts for norbornene polymerization. Moreover, 2a – d are also active ethylene–norbornene (E–N) copolymerization catalysts. The incorporation of norbornene in the E–N copolymer could be controlled by varying the charged norbornene. ¹³C NMR analyses showed the microstructures of the E–N copolymers were predominantly alternated and isolated norbornene units in copolymer, dyad, and triad sequences of norbornene were detected in the E–N copolymers with high incorporated content of norbornene. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 93–101, 2008     

Highly active ethylene polymerization and copolymerization with norbornene using bis(imino‐indolide) titanium dichloride–MAO system

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 M_w 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     

Effect of substituents on addition polymerization of norbornene derivatives with two Me3Si-groups using Ni(II)/MAO catalyst

Addition polymerization and copolymerization of bis(Me₃Si)-substituted norbornene-type monomers such as 5,5-bis(trimethylsilyl)norbornene-2, 2,3-bis(trimethylsilyl)norbornadiene-2,5 and 3,4-bis(trimethylsilyl)tricyclo[4.2.1.0^2,5]nonene-7, in the presence of Ni(II) naphtenate/MAO catalyst were studied. Disubstituted norbornene and norbornadiene were found to be practically inactive in homopolymerization. On the other hand, their copolymerization with norbornene proceeded with moderate yields of copolymers containing predominantly norbornene units. Under studied reaction conditions 2,3-bis(trimethylsilyl)norbornadiene-2,5 was transformed into the only exo-trans-exo-dimer as a result of the [2+2]-cyclodimerization reaction. Moving Me₃Si-substituents one carbon atom away from norbornene double bond made 3,4-bis(trimethylsilyl)tricyclo[4.2.1.0^2,5]nonene-7 active in homopolymerization and allowed to obtain addition homo-polymer with two Me₃Si-substituents in each elementary unit. The reaction mechanism and steric effect of Me₃Si-substituents are also discussed.     

Homopolymerization and copolymerization of vinyl chloride over supported metalorganic catalysts

The homopolymerization of vinyl chloride and its copolymerization with ethylene over dibutyl ether–modified SiO₂-supported Ziegler–Natta catalysts based on titanium and vanadium chlorides have been studied. The supported metal complexes are sufficiently active in the polymerization of vinyl chloride. Their activity depends on the catalyst composition and conditions of formation of the catalyst on the surface of the support. The chain structure of the resulting polyvinyl chloride (PVC) has been studied by NMR spectroscopy. The thermal properties of the synthesized PVC have been investigated by differential scanning calorimetry. The PVC obtained possesses enhanced thermal stability owing to the specific features of its chain structure. Vinyl chloride polymerization over the supported metalorganic catalyst proceeds mainly via a free-radical mechanism. Process conditions have been found for conducting the copolymerization of vinyl chloride with ethylene over supported metal complexes resulting in the formation of true statistical copolymers, which is confirmed by IR and NMR spectroscopy.     

Group 4 dimethylsilylenebisamido complexes bearing the 6-[2-(diethylboryl)phenyl]pyrid-2-yl motif: synthesis and use in tandem ring-opening metathesis/vinyl-insertion copolymerization of cyclic olefins with ethylene

Two novel Zr(IV)- and Hf(IV)-based bisamido complexes bearing the 6-[2-(diethylboryl)phenyl]pyrid-2-yl motif, that is, [ZrCl(2){Me(2)Si(DbppN)(2)}(thf)] (9) and [HfCl(2){Me(2)Si(DbppN)(2)}(thf)(2)] (10) (DbppN=6-[2-(diethylboryl)phenyl]pyridine-2-amido) have been prepared. Their reactivities have been compared with that of a model precatalyst that does not bear the aminoborane motif. Upon activation with methylalumoxane, precatalysts 9 and 10 are active in the homopolymerization of ethylene (E) yielding high-density polyethylene (HDPE). In the copolymerization of E with cyclopentene (CPE), for example by the action of 9, the presence of CPE resulted in a dramatic increase in the polymerization activity of E, while CPE incorporation remained close to or at zero. In the vinyl-insertion copolymerization of norborn-2-ene (NBE) with E by the action of 9, statistical cyclic olefin copolymers of these two monomers were obtained. At higher NBE concentrations, however, 9 gave rise to reversible ring-opening metathesis (ROMP)/vinyl-insertion polymerization (VIP) of NBE with E, resulting in the formation of multi-block copolymers of the general formula poly(NBE)(ROMP)-co-poly(NBE)(VIP)-co-poly(E). This particular feature of precatalyst 9, that is, the ability to induce a reversible α-H elimination/α-H addition reaction, is attributed to the unique role of the 6-[2-(diethylboryl)phenyl]pyrid-2-yl ligand. Accordingly, a model precatalyst lacking this ligand does not have the ability to induce α-H elimination/α-H addition reactions. The different (11)B NMR shifts of various diethylborylphenylpyrid-2-ylamines and -amides permit a ranking of the strengths of the B-N bonds in these compounds. This strength of the B-N bond is correlated with the propensity of 9/MAO to produce poly(NBE)(ROMP)-co-poly(NBE)(VIP)-co-poly(E) at different temperatures.