氧对n-BuLi/THF引发丁二烯苯乙烯共聚合的影响

研究了氧分子与活性种快速失活的定量关系 ,二代杂质对活性种及聚合物微观结构的影响 .从聚合动力学及聚合物相对分子质量等方面来测定氧分子快速杀死活性种数 ,并考察了体系中氧产生的偶联反应及其对丁苯共聚物物理机械性能、动态力学性能及耐磨性能的影响 .结果表明 :氧对n BuLi THF体系丁苯共聚合有不利影响 .     

SAPO-34分子筛催化丁烯转化制丙烯的研究

通过水热法合成SAPO-34分子筛,将其制成催化剂用于催化丁烯转化制取丙烯,考察了反应温度、空速和铝磷比等对催化性能的影响;还比较了SAPO-34分子筛与ZSM-5分子筛催化该反应的差异.结果表明,在实验范围内,反应温度升高会使得丁烯的转化率明显增高,且丙烯选择性提高;而空速增加,则丁烯的转化率和丙烯选择性降低;铝磷比越大,对丙烯的选择性越差.在有效的反应时间内,SAPO-34分子筛催化效果好于ZSM-5分子筛,但单程寿命较ZSM-5分子筛短.     

Kinetic features of ethylene polymerization over supported catalysts [2,6‐bis(imino)pyridyl iron dichloride/magnesium dichloride] with AlR3 as an activator

The effects of polymerization temperature, polymerization time, ethylene and hydrogen concentration, and effect of comonomers (hexene‐1, propylene) on the activity of supported catalyst of composition LFeCl₂/MgCl₂‐Al(i‐Bu)₃ (L = 2,6‐bis[1‐(2,6‐dimethylphenylimino)ethyl] pyridyl) and polymer characteristics (molecular weight (MW), molecular‐weight distribution (MWD), molecular structure) have been studied. Effective activation energy of ethylene polymerization over LFeCl₂/MgCl₂‐Al(i‐Bu)₃ has a value typical of supported Ziegler–Natta catalysts (11.9 kcal/mol). The polymerization reaction is of the first order with respect to monomer at the ethylene concentration >0.2 mol/L. Addition of small amounts of hydrogen (9–17%) significantly increases the activity; however, further increase in hydrogen concentration decreases the activity. The IRS and DSC analysis of PE indicates that catalyst LFeCl₂/MgCl₂‐Al(i‐Bu)₃ has a very low copolymerizing ability toward propylene and hexene‐1. MW and MWD of PE produced over these catalysts depend on the polymerization time, ethylene and hexene‐1 concentration. The activation effect of hydrogen and other kinetic features of ethylene polymerization over supported catalysts based on the Fe (II) complexes are discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5057–5066, 2007     

丙烯酰胺在聚乙二醇水溶液中聚合初期的液滴形成与成长过程

用动态激光光散射(DLS)在线观测了丙烯酰胺(AM)在聚乙二醇(PEG)水溶液中聚合初期液滴的出现、生长及聚并过程,考察了PEG分子量和浓度对聚合初期液滴尺寸的影响;用透射电镜(TEM)对聚合初期液滴形态的演变进行了观察,发现与DLS结果能很好吻合.用分光光度计对聚合体系分相点进行确定,采用溴化法测定了聚合体系临界分相时的转化率.随PEG分子量或浓度的升高,临界分相转化率逐渐减小;随温度的升高,临界分相转化率先减小后增大,在50℃左右出现最小值.用凝胶渗透色谱(GPC)对聚合体系临界分相时聚丙烯酰胺(PAM)的分子量进行了研究,变化趋势与临界分相转化率的变化一致.在上述基础上,提出了AM在PEG水溶液中聚合初期的液滴形成、成长机理.     

The effect of molecular weight and catalyst concentration on catalytic activity in mechanochemically activated transesterification using silver(I)‐N‐heterocyclic carbene latent catalysts

We have investigated the effect of the concentration and molecular weight on the activity of polymeric silver(I)‐NHC (NHC = N‐heterocyclic carbene) catalyst complexes in ultrasound‐induced mechanochemical catalyst activation. A strong dependence of the turnover number (TON) on initial catalyst concentration was observed in the transesterification of vinyl acetate with benzyl alcohol. The main findings of this study are that the concentration and molecular weight effects on TON are caused by competition between mechanochemical catalyst activation and deactivation, most likely by reactive species produced during the sonication process. Performing the transesterification reaction under radical‐suppressing conditions resulted in a significant increase of TON. This result clearly demonstrates the increased catalyst lifetime when reducing the amount of sonochemical impurities, and it highlights the importance of controlling and suppressing secondary, sonochemical processes when using ultrasound‐induced mechanochemical generation of reactive species such as catalysts. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

THE INFLUENCE OF SUBSTITUENTS IN METALLOCENE ON PROPYLENE POLYMERIZATION*

Two new unbridged zirconocenes, bis(2,4,7-trimethyl indenyl)zirconium dichloride (Met-Ⅰ) andbis(2-methyl-4,7-diethyl indenyl)zirconium dichloride (Met-Ⅱ) were prepared in order to investigate thesteric effects of substituents on the nature of the catalysts for the polymerization of propylene. A mixture ofmethyl aluminoxane (MAO) and triisobutylaluminum [Al(iBu)_3] was used as cocatalyst to activate thesecatalysts. The decrease in steric bulkiness of substituents at 4 and 7 positions of the indenyl ring resulted inan increase of both activity and molecular weight as well as the isotacticity.     

双金属氧联醇盐催化环硫丙烷的开环聚合

研究了环硫丙烷以铝锌双金属氧联醇盐为催化剂在甲苯中的聚合动力学及分子量分布。结果表明,环硫丙烷的聚合速度对单体浓度是二级关系,对催化剂浓度是半级关系。聚合系统中催化剂存在缔合,认为环硫丙烷以双分子配位增长。测得聚合活化能为12.2±0.5kcal/mol,计算了单体及溶剂的链转移常数。通过淋洗液中加氯化锂的GPC工作研究了分子量及其分布随转化率的变化。     

Olefin copolymerization with metallocene catalysts. I. Comparison of catalysts

A number of metallocene/methylaluminoxane (MAO) catalysts have been compared for ethylene/propylene copolymerizations to find relationship between the polymerization activities, copolymer structures, and copolymerization reactivity ratio with the catalyst structures. Stereorigid racemic ethylene bis (indenyl) zirconium dichloride and the tetrahydro derivative exhibit very high activity of 10 ⁷ g (mol Zr h bar)^?1, giving copolymers having comonomer compositions about the same as the feed compositions, molecular weights increasing with the increase of ethylene in the feed, random incorporation of comonomers, and narrow molecular weight distribution indicative of a single catalytic species. Nonbridged bis (indenyl) zirconium behaved differently, favoring the incorporation of ethylene over propylene, producing copolymers whose molecular weight decreases with the increase of ethylene in the feed, broad molecular weight distribution, and a methanol soluble fraction. This catalyst system contains two or more active species. Simple methallocene catalysts have much lower polymerization activities. C_pTiCl₂/MAO produced copolymers with tendency toward alternation, whereas Cp₂HfCl₂/MAO gave copolymer containing short blocks of monomers.     

Homo-polymerization of alpha-olefins and co-polymerization of higher alpha-olefins with ethylene in the presence of CpTiCl2(OC6H4X-p)/MAO catalysts (X = CH3, Cl)

Cyclopentadienyl-titanium complexes containing -OC6H4X ligands (X = Cl,CH3) activated with methylaluminoxane (MAO) were used in the homo-polymerization of ethylene, propylene, 1-butene, 1-pentene, 1-butene, and 1-hexene, and also in co-polymerization of ethylene with the alpha-olefins mentioned. The -X substituents exhibit different electron donor-acceptor properties, which is described by Hammett's factor (sigma).The chlorine atom is electron acceptor, while the methyl group is electron donor. These catalysts allow the preparation of polyethylene in a good yield. Propylene in the presence of the catalysts mentioned dimerizes and oligomerizes to trimers and tetramers at 25 degrees C under normal pressure. If the propylene pressure was increased to 7 atmospheres,CpTiCl2(OC6H4CH3)/MAO catalyst at 25 degrees gave mixtures with different contents of propylene dimers, trimers and tetramers. At 70 degrees C we obtained only propylene trimer.Using the catalysts with a -OC(6)H(4)Cl ligand we obtained atactic polymers with M(w) 182,000 g/mol (at 25 degrees C) and 100,000 g/mol (at 70 degrees C). The superior activity of the CpTiCl2(OC6H4Cl)/MAO catalyst used in polymerization of propylene prompted us to check its activity in polymerization of higher alpha-olefins (1-butene, 1-pentene, 1-hexene)and in co-polymerization of these olefins with ethylene. However, when homo-polymerization was carried out in the presence of this catalyst no polymers were obtained. Gas chromatography analysis revealed the presence of dimers. The activity of the CpTiCl2(OC6H4Cl)/MAO catalyst in the co-polymerization of ethylene with higher alpha-olefins is limited by the length of the co-monomer carbon chain. Hence, the highest catalyst activities were observed in co-polymerization of ethylene with propylene (here a lower pressure of the reagents and shorter reaction time were applied to obtain catalytic activity similar to that for other co-monomers). For other co-monomers the activity of the catalyst decreases as follows: propylene >1-butene > 1-pentene > 1-hexene. In the case of co-polymerization of ethylene with propylene, besides an increase in catalytic activity, an increase in the average molecular weight M(w) of the polymer was observed. Other co- monomers used in this study caused a decrease of molecular weight. A significant increase in molecular weight distribution (M(w)/M(n)) evidences a great variety of polymer chains formed during the reaction.     

单茂钛/MAO体系催化乙烯/丙烯共聚合研究Ⅰ.乙烯/丙烯共聚物的合成及聚合反应规律研究

采用合成的催化剂五甲基环戊二烯基三烯丙氧基钛 [Cp Ti(OAllyl) 3]与改性甲基铝氧烷 (mMAO)组成新型催化体系进行乙烯 /丙烯共聚合 ,考察了助催化剂 (mMAO)中TMA含量、气体配比、聚合温度、助催化剂和主催化剂浓度等因素对共聚合活性及产物分子量的影响 ,研究其变化规律 .结果表明 ,Cp Ti(OAllyl) 3/mMAO催化体系中钛的价态分布为Ti(Ⅳ )时对共聚合更为有利 ,制得了乙烯 /丙烯无规共聚物弹性体     

Ethylene and propylene polymerization behavior of a series of bis(phenoxy–imine)titanium complexes

This contribution reports ethylene and propylene polymerization behavior of a series of Ti complexes bearing a pair of phenoxy–imine chelate ligands. The bis(phenoxy–imine)Ti complexes in conjunction with methylalumoxane (MAO) can be active catalysts for the polymerization of ethylene. Unexpectedly, this C₂ symmetric catalyst produces syndiotactic polypropylene. ¹³C NMR spectroscopy has revealed that the syndiotacticity arises from a chain-end control mechanism. Substitutions on the phenoxy–imine ligands have substantial effects on both ethylene and propylene polymerization behavior of the complexes. In particular, the steric bulk of the substituent ortho to the phenoxy–oxygen is fundamental to obtaining high activity and high molecular weight for ethylene polymerization and high syndioselectivity for the chain-end controlled propylene polymerization. The highest ethylene polymerization activity, 3240 kg/mol-cat h, exhibited by a complex having a t-butyl group ortho to the phenoxy–oxygen, represents one of the highest reported to date for Ti-based non-metallocene catalysts. Additionally, the polypropylene produced exhibits a T_m, 140 °C, and syndioselectivity, rrrr 83.7% (achieved by a complex bearing a trimethylsilyl group ortho to the phenoxy–oxygen) that are among the highest for polypropylenes produced via a chain-end control mechanism. Hence, the bis(phenoxy–imine)Ti complexes are rare examples of non-metallocene catalysts that are useful for the polymerization of not only ethylene but also propylene.     

RING-OPENING POLYMERIZATION OF PROPYLENE SULFIDE CATALYZED BY BIMETALLIC OXO ALKOXIDE

It was shown that the polymerization rate of propylene sulfide is second order with respect tomonomer concentration and half order with respect to catalyst concentration. A mechanism ofbimolecular coordinated propagation of propylene sulfide and association of the catalyst in thepolymerization system were proposed. The activation energy of polymerization was measured as12.2±0. 5 kcal/mole. Chain transfer constants of monomer and solvent were calculated. Thechange of molecular weight and molecular weight distribution with conversion was followed by GPCwhich was improved by adding LiCl to eluant.     

聚合物对非离子十二烷基聚氧乙烯聚氧丙烯醚浊点的影响

测定了水溶性高分子聚乙二醇(PEC1000、PEG2000、PEG6000)和聚乙烯吡咯烷酮(PVP-K30、PVP-K90)对三种非离子表面活性剂十二烷基聚氧乙烯聚氧丙烯醚C12H25O(EO)m(PO)nH(LS36,m=3,n=6;LS5,m=4,n=5;LS54,m=5,n=4)浊点的影响.结果表明,聚乙二醇(PEG)可使三种表面活性剂水溶液浊点降低;而聚乙烯吡咯烷酮(PVP)随其浓度增加,表面活性剂溶液浊点先升高然后又下降;浊点下降程度与聚合物浓度和分子量有关.     

Anionic synthesis of poly[ethylene methylene bis(4-phenyl-carbamate)-g-acrylonitrile]

A relatively high-molecular-weight polyurethane based on MDI and ethylene glycol was prepared and characterized. This polymer was metalated with sodium hydride in N,N-dimethylformamide (DMF) at about 0°C. Metalation was confirmed principally by spectroscopic identification of the N-methyl derivative obtained by coupling the metalated polymer with methyl iodide. Under appropriate reaction conditions the metalated polyurethane was used for the anionic graft polymerization of the reactive monomers acrylonitrile and ethylene and propylene sulfides. Attempted anionic graft polymerizations with other monomers, including styrene and ethylene and propylene oxides, were unsuccessful. The polyurethane grafted with acrylonitrile was separated by fractionation from accompanying small amounts of polyacrylonitrile, a low-molecular-weight homopolymer. One sample of polyurethane grafted with acrylonitrile was identified by microanalysis, IR, NMR, and increase in weight and was also characterized by differential thermal analysis.     

活性氧化铝柱-气相色谱法测定工作场所空气中“四烯”的方法研究

采用活性氧化铝柱-气相色谱法对作业场所空气中乙烯、丙烯、丁烯、丁二烯进行活性炭采样,热解吸后进样分析。活性炭管对"四烯"的吸附性良好,测定结果的相对标准偏差为0.37%～2.08%;乙烯、丙烯、丁烯、丁二烯检出限分别为0.0010、0.000520、.00083、0.0003 mg/L;样品的平均解吸效率为93.7%～98.59%;样品的平均采样效率为93.9%～99.1%;乙烯、丙烯、丁烯、丁二烯穿透容量分别为9.58、.87、.4、7.1 mg;样品在室温下放置7 d,其平均样品损失率不大于5.58%,在4～10℃环境放置10 d,其平均样品损失率不大于7.11%,空气中乙烷对本方法无干扰。该法可满足职业卫生检测的要求。     

FI catalysts: new olefin polymerization catalysts for the creation of value-added polymers

This contribution reports the discovery and application of phenoxy-imine-based catalysts for olefin polymerization. Ligand-oriented catalyst design research has led to the discovery of remarkably active ethylene polymerization catalysts (FI Catalysts), which are based on electronically flexible phenoxy-imine chelate ligands combined with early transition metals. Upon activation with appropriate cocatalysts, FI Catalysts can exhibit unique polymerization catalysis (e.g., precise control of product molecular weights, highly isospecific and syndiospecific propylene polymerization, regio-irregular polymerization of higher alpha-olefins, highly controlled living polymerization of both ethylene and propylene at elevated temperatures, and precise control over polymer morphology) and thus provide extraordinary opportunities for the syntheses of value-added polymers with distinctive architectural characteristics. Many of the polymers that are available via the use of FI Catalysts were previously inaccessible through other means of polymerization. For example, FI Catalysts can form vinyl-terminated low molecular weight polyethylenes, ultra-high molecular weight amorphous ethylene-propylene copolymers and atactic polypropylenes, highly isotactic and syndiotactic polypropylenes with exceptionally high peak melting temperatures, well-defined and controlled multimodal polyethylenes, and high molecular weight regio-irregular poly(higher alpha-olefin)s. In addition, FI Catalysts combined with MgCl(2)-based compounds can produce polymers that exhibit desirable morphological features (e.g., very high bulk density polyethylenes and highly controlled particle-size polyethylenes) that are difficult to obtain with conventionally supported catalysts. In addition, FI Catalysts are capable of creating a large variety of living-polymerization-based polymers, including terminally functionalized polymers and block copolymers from ethylene, propylene, and higher alpha-olefins. Furthermore, some of the FI Catalysts can furnish living-polymerization-based polymers catalytically by combination with appropriate chain transfer agents. Therefore, the development of FI Catalysts has enabled some crucial advances in the fields of polymerization catalysis and polymer syntheses.     

VOCl_3/Et_3Al_2Cl_3/CCl_4溶剂体系催化乙烯丙烯共聚

本文以VOCl_3/Et_3Al_2Cl_3为催化剂,在CCl_4溶剂中进行乙烯共聚反应。在聚合过程中,发生一异常的颜色突变现象。颜色突变后,体系催化聚合生成分子量很低的产物。从聚合物的结构表征及机理探讨表明:颜色突变后,体系产生了新的活性中心,催化机理发生了转变——由配位机理转变为阳离子机理。     

TiCl4共引发异丁烯正离子聚合合成反应活性聚异丁烯

由H2O/TiCl4/甲醇或乙醚体系引发异丁烯在二氯甲烷与己烷混合溶剂中进行正离子聚合,探讨甲醇用量、聚合时间等因素对正离子聚合以及产物分子量、分子量分布和末端基结构的影响,并在此基础上探讨TiCl4共引发混合C4馏分中异丁烯选择性正离子聚合以制备活性聚异丁烯的可行性.结果表明,含氧试剂对聚合反应起到明显的调节作用,可适当稳定碳正离子活性中心,降低链增长速率,降低聚合产物的分子量(Mn=1600~4600),使分子量分布明显变窄(Mw/Mn=1.35~2.05),并可调节大分子链末端基结构及其含量.降低聚合体系中微量单体浓度以及适当延长聚合反应时间,均有利于提高聚异丁烯大分子链末端α-双键结构含量.通过TiCl4共引发异丁烯正离子聚合制备出末端α-双键含量可以达到70%以上的低分子量高反应活性聚异丁烯.此外,该引发体系还可引发混合C4馏分原料中异丁烯进行高选择性正离子聚合,得到Mn=2000、Mw/Mn=2.59、端基α-双键含量为38.9%的聚异丁烯.     

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene. IV. Effects of emulsifier concentration and dose rate

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene was carried out by batch operation with an initial molar ratio of tetrafluoroethylene to propylene of 3.0 in the emulsifier concentration range of 0.1 to 3.0% and in the dose rate range of 2 × 10⁴ to 2 × 10⁵ R/hr. The effects of emulsifier concentration and dose rate on the polymerization rate and the number-average degree of polymerization are discussed in comparison with the Smith-Ewart theory. The polymerization rate is proportional to the 0.26 power of emulsifier concentration and to the 0.7 power of dose rate. The degree of polymerization is independent of the emulsifier concentration and the dose rate above the critical micelle concentration (CMC) of the emulsifier. These results are not in agreement with the Smith-Ewart theory. It is explained that the termination reaction is a degradative chain transfer of propagating radicals to propylene. On the other hand, the copolymerization in emulsion occurs either below the CMC or in the absence of emulsifier. Under these conditions, however, it is impossible to obtain a copolymer of high molecular weight at a high rate of polymerization because of the presence of a small number of polymer particles formed and the short interval of chain growth in the polymer particle.     

Reaction of Lithium Cellulosate with Episulfides

The reactions of propylene, ethylene, and styrene sulfide with cotton fabrics in the form of their lithium cellulosate derivative, obtained by metallation with lithium methoxide, were studied. Both graft and homo-polymerization took place and in the reaction with propylene and ethylene sulfide, cotton fabrics with high polysulfide content were obtained. With propylene sulfide 50% of the monomer polymerized was grafted. The effects of monomer concentration, cellulosate degree of substitution, reaction time, and solvent on the polymerization were investigated. In contrast with propylene and ethylene sulfide, only small conversions were obtained in the reaction with styrene sulfide. The results were attributed to steric effects.