均相定向聚合的某些进展

如众周知,典型的齐格勒-纳达(Ziegler-Natta)定向聚合催化剂是多相系統。由于催化系統的这一特点,使得在聚合及聚合物純制过程中,出現了一系列理論和实际問題,其中值得一提的是:难以从聚合物中洗出残存的催化剂以及对聚合过程本身研究所带来的困难等。为了克服非均相定向聚合催化剂的这些缺点,近年来出现了不少有关均相定向聚合方面的研究工作,因为采用均相絡合物催化系統不只可以大大减少催化剂的用量,而且可以简化所得聚合物的純化过程。虽然目前有关均相定向聚合的工作,文献上有过不少的报导,但按其引发的性质来說,大致可分为两类:一     

稀土定向聚合络合催化剂的研究

定向聚合所用的络合催化剂,过去只限于元素周期表中带有d电子的Ⅳ—Ⅷ族过渡金属元素。经过多年的探索研究,我们发现了新的一类定向聚合稀土络合催化剂。稀土络合催化剂在双烯烃的均聚和共聚中具有相当高的催化活性,特别良好的定向效应,所得聚丁二烯、聚异戊二烯及其共聚物的顺-1,4结构的含量达94％以上,并且性能优良。本文叙述了稀土络合催化剂的组成,稀土元素、烷基铝和第三组分等的变化对稀土络合催化剂的活性和定向性的影响,以及稀土络合催化聚合的某些机理。     

稀土络合催化乙炔定向聚合

本文首次研究了应用稀土化合物作乙炔定向聚合催化剂,发现除钷外所有15个镧系元素的环烷酸盐或2-乙基己基膦酸盐与三烷基铝组合成的络合催化剂都可以使乙炔定向聚合。其特点是乙炔在室温(30℃～0℃)下聚合,便能制得高顺式(80％～100％)、具有金属光泽的银灰色聚乙炔薄膜,显示稀土络合催化剂是一类合成高顺式聚乙炔极其方便的优良催化剂。本文报道乙炔在膦酸稀土盐和环烷酸稀土催化剂中定向聚合特征,以及用红外光谱、热分析、顺磁共振、X衍射、扫描电子显微镜及电阻率测定等对所制备的稀土聚乙炔薄膜初步表征的结果。     

丁二烯在含有机镁铝络合物稀土催化剂中的聚合

本文研究定向稀土催化剂组份中引入镁铝络合物后对丁二烯聚合的影响。改变镁铝络合物与氯化物的种类和用量,皆明显的影响其聚合活性。当催化剂中含有苯基镁的烷基铝络合物时,聚丁二烯反-1,4链节可达36%。选择适当的催化剂组成和配比时,含镁稀土定向催化剂具有较高的聚合活性。     

有机/无机纳米杂化材料载体化钛催化剂的聚合研究Ⅱ.间同聚苯乙烯制备

定向聚合;有机/无机纳米杂化材料载体化钛催化剂的聚合研究Ⅱ.间同聚苯乙烯制备     

丙烯聚合催化剂的研究进展

自从上个世纪五十年代发现Ziegler-Natta催化剂以来，对丙烯定向聚合的研究一直没有中断过．五十年来，聚丙烯催化剂从低活性、低规整性的第一代TiCl3催化剂已经发展到了第四代超高活性和高定向性的球形大颗粒催化剂，近年来又发现茂金属是有效的丙烯聚合催化剂．茂金属有清晰的组成和立体结构，这为研究结构和性能的关系带来了方便，因而在学术界和企业界引起了新一轮对聚丙烯合成研究的兴趣．本文对负载型经典Ziegler-Natta催化体系和茂金属催化体系催化丙烯聚合的研究进展作一个综述．     

含稀土钛系催化剂的苯乙烯高活性定向聚合研究

本文用新研制的含稀土钕化合物的钛系催化剂(SN-1催化剂)于苯乙烯在苯溶液中进行定向聚合,能同时使产率、等规度、催化效率与聚合速率四项指标得到提高并远超过文献值。研究了各种聚合条件,即催化剂浓度、苯乙烯单体浓度、助催化剂三乙基铝浓度和聚合温度各因素对于催化效率、聚苯乙烯产率、等规度和分子量的影响规律并作讨论。     

稀土定向聚合催化剂及用以聚合的二烯类高聚物的特征

十五年前,我们曾首先报导了用镧系稀土化合物作为丁二稀的定向聚合催化剂,得到了顺-1,4-构型的含量高的聚丁二烯,这在Eiegler-Natta型催化剂中从利用d-轨道成键电子发展f-电子。当时所用催化剂为二元体系,后由Throckmorton改进成三元体系、聚合活性得以提高。之后,我们用三元体系对异戊二烯进行了定向聚合,也得到了顺式含量高的聚异戊二烯。近年来,我们对这类催化体系的定向性、催化聚合活性、聚合反应历程及动力学等方面,以及上述这两种均聚物在结构与性能方面的特点进行了研究。同时还发展了丁二烯和异戊二烯的共聚,两种链节的顺式含量都高,并在催化剂上从三元再发展到新的二元体系,其中一些代表性结果如下。     

~(13)C-NMR研究高效载体催化剂丙烯立体定向聚合反应机理

<正> 自从用C-NMR技术对聚丙烯进行测定,得到了分辨力良好的聚丙烯甲基碳区域的核磁共振谱后,引起了聚丙烯研究者的极大兴趣,迅速开展了应用核磁共振技术来研究聚丙烯分子链的构型和立体定向聚合机理,众所周知,用不同催化剂体系进行丙烯聚合,得到的聚合物链结构不同,聚合机理也有所差别。Zambelli等认为用Ziegler-Natta型催化剂体系聚合得到的聚丙烯,其聚合机理属于催化剂活性中心控制的单活性中心模型。Yoshio Inoue等用TiCl_4/MgCl_2/C_6H_5COOC_2H_5-AlEt_3 催化剂体系进行丙烯聚合,     

络合催化合成橡胶研究二十年

五十年代中期,在高分子领域里出现了Ziegler-Natta型络合催化剂,在其存在下的单体聚合的过程是立体有择的(定向聚合),所得聚合物的链具有规整的立体或几何构型。定向聚合的出现引起了高分子学科和高分子工业的革命。兴起许多前所未有的通用橡胶、塑料新品种;在学科上对催化剂结构、聚合机理、聚合物     

HIGHLY ACTIVE CATALYTIC STEREOSPECIFIC POLYMERIZATION OF STYRENE

A novel highly active catalyst of TiCl_4/MgCl_2--Al(C_2H_5), system (called SN-1 catalyst, in whichrare earth compound NdCl_3, is included) was used for studying stereospecific polymerization of styrenein benzene solution. Highly isotactic polystyrene was prepared with far better yield and higher cataly-tic efficiency than the results ever reported in literatures. The influences of concentration of mono-mer, catalyst, triethyaluminum as well as polymerization temperature on the catalytic efficiency, yield,tacticity and molecular weight of polystytene have been investigated.     

Molecular sieves supported recyclable catalyst for atom transfer radical polymerization using hydration approach

Molecular Sieves (MS) were used as a recyclable support for atom transfer radical polymerization. The catalyst complex, CuBr₂/ligand was supported on hydrated MS and used for the polymerization of benzyl methacrylate at room temperature in anisole. The polymerization using CuBr₂/PMDETA (pentamethyl diethyltetraamine) catalyst that is physically held by the hydration of MS exhibited moderate control and produced catalyst free polymers (<0.1 ppm) with narrow molecular weight distribution (M_w/M_n ≤ 1.33). The polymerization occurred at the interface between the hydrated support and the solution containing initiator and monomer. The hydrated MS supported catalyst was recycled efficiently without a significant loss in activity. The polymerization proceeded in a “living”/controlled manner as was evident from first‐order time conversion plots. The split kinetics experiment affirmed that there was no propagation in the solution in the absence of the supported catalyst. The reaction order plot showed zero‐order dependence on the bulk initiator concentration in solution. The results of MS supported catalyst were compared to Na‐clay supported catalyst system and the improved results were attributed to high self‐diffusion coefficient and low diffusion activation energy of water on its surface. Published 2017.^§ J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3875–3883     

Catalyseurs Zieger-Natta supportés sur MgCl2 pour la polymérisation stéréorégulée du propène. II. Système catalytique simple: Solide binaire MgCl2-TiCl4 et solution cocatalytique triéthylaluminium,benzoate d'ethyle

The kinetics of propene polymerization in heptane slurry at 1–4 bars was studied with a catalytic system that consisted of a solid catalyst prepared by adsorption of TiCI₄ on pure porous MgCl₂ (by dehydrating MgCl₂, 6 H₂O with thionyl chloride) and a cocatalytic, heptanic solution of ethylbenzoate (BE) and triethylaluminium (TEA). At a temperature approaching 60°C/polymerization began immediately after the introduction of the monomer. The polymerization rate decreased continuously during the reaction. The loss in activity, however, was not due to a diffusional effect (e.g., blocking of the catalyst by the growing polymer). Studies of the ageing of the catalytic system showed a deactivation of the catalytic system itself as a function of the time of contact between the catalyst and the cocatalyst. The product of the thermal decomposition of the complex 1:2 formed by the reaction of BE with TEA was not associated with the deactivation process or stereospecific control, which depend on the BE/AI ratio and the presence of the complex.     

CYCLOPOLYMERIZATION OF DIPROPARGYL DERIVATIVES BY Cp2MoCl2-EtAlCl2 CATALYST SYSTEM

ABSTRACT

A Cp₂MoCl₂-EtAlCl₂ catalyst system was used for the cyclopolymerization of various dipropargyl derivatives having different functionalities. These catalyst systems were found to be very effective for the polymerization of some dipropargyl monomers to give a relatively high yield of polymer. The polymerization behaviors were strongly dependent on the functionalities of dipropargyl monomers. The polymerization of such dipropargyl monomers as 1,6-heptadiyne, diphenyldipropargyl methane, diethyldipropargyl malonate, etc. proceeded well to give a quantitative yield, whereas this catalyst system was found to be less effective for the polymerization of dipropargyl monomers having perfluoroalkyl groups and quaternary ammonium salts. The polymer structure of the resulting polymers was characterized by various instrumental methods such as NMR, IR, and UV-visible spectroscopies to have a conjugated polyene backbone system with cyclic recurring units. The portion of 5- and 6-membered rings of the present conjugated cyclopolymer were also discussed.     

引发甲基丙烯酸甲酯聚合的聚丙烯酰胺－氯化铜配合物膜催化剂表征

考察甲基丙烯酸甲酯在室温Ｎａ２ＳＯ３水溶液的聚合能力，发现在该溶液添加聚丙烯酰胺（ＰＡＡｍ）－氯化铜（ＣｕＣｌ２）配合物膜以组成ＰＡＡｍ－ＣｕＣｌ２膜／Ｎａ２ＳＯ３催化引发系是必不可少的，采用ＥＳＲ、ＩＲ、ＸＰＳ和电导率等手段研究该体系催化剂的表面结构，结果表明，膜的单位面积平均含铜量在一定范围内和配位体种类等对催化活性有显著影响，即催化性能与催化剂的表面结构紧密相关。     

Polymerization of acrylonitrile with VCl4–Al(C2H5)3 catalyst system in presence of acetonitrile

The polymerization of acrylonitrile with the homogeneous catalyst system of VCl₄–AlEt₃ in acetonitrile at 40°C has been investigated. The rate of polymerization is found to be first-order with respect to monomer and inversely proportional to the catalyst concentration. The overall activation energy for this catalyst system is 10.97 kcal/mole. The inverse proportionality of rate of polymerization with the catalyst concentration is attributed to the permanent complex formation between the catalyst complex and acrylonitrile, and a reaction scheme is proposed.     

Nitrogen-containing organozinc and organoaluminum as catalyst for stereospecific polymerization of propylene oxide

Catalytic activities of the reaction products of diethylzinc or triethylaluminum with primary amines in the polymerization of propylene oxide were studied. Generally, organozinc compounds give higher ratio of the crystalline to the amorphous polymer than the organoaluminums. In the reactions of organometallic compounds with primary amines, Et₂AlNPhAlEt₂, Et₂AlN-t-BuAlEt₂, EtZnNH-t-Bu, and EtZn-t-BuZnEt were isolated in crystalline state. EtZnN-t-BuZnEt proved to be an excellent catalyst for the stereospecific polymerization of propylene oxide and forms coordination complexes with some electron donors such as dioxane, pyridine, epichlorohydrin and propylene oxide. The propylene oxide complex is unstable in solution and decomposes at temperatures above room temperature to give poly(propylene oxide), while the pyridine complex has no catalytic activity. Therefore, it is concluded that the polymerization of propylene oxide with this catalyst proceeds through the coordination of propylene oxide to the zinc atom of the catalyst.     

二异丁基锌控制高密度聚乙烯分子量的研究

本文报告了TiCl_4-MgCl_2-AlCl_3/Al(i-Bu)_3-Zn(i-Bu)_2催化体系的乙烯聚合反应中,二异丁基锌对产物分子量和聚合活性的影响。结果表明:在适宜的聚合条件下,二异丁基锌可以有效地控制产物的分子量。     

A copper‐based reverse atom‐transfer radical polymerization process for the living radical polymerization of polyacrylonitrile

The reverse atom‐transfer radical polymerization (RATRP) technique using CuCl₂/2,2′‐bipyridine (bipy) complex as a catalyst was applied to the living radical polymerization of acrylonitrile (AN). A hexasubstituted ethane thermal iniferter, diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate (DCDPS), was firstly used as the initiator in this copper‐based RATRP initiation system. A CuCl₂ to bipy ratio of 0.5 not only gives the best control of molecular weight and its distribution, but also provides rather rapid reaction rate. The rate of polymerization increases with increasing the polymerization temperature, and the apparent activation energy was calculated to be 57.4 kJ mol^?1. Because the polymers obtained were end‐functionalized by chlorine atoms, they were used as macroinitiators to proceed the chain extension polymerization in the presence of CuCl/bipy catalyst system via a conventional ATRP process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 226–231, 2006     

ANIONIC POLYMERIZATION WITH COMPLEX BASE. I. POLYMERIZATION OF PHENYLISOCYANATE

In this work, phenylisocyanate was polymerized in bulk and in a solution of THF by the complex base (CB), NaNH₂/(CH₃)₃CONa catalyst under vacuum. The percent yield for bulk polymerization at ?20°C first increased with a slow rate reaching 32% conversion in 3 hours, then with a greater rate up to 86% in 6 hours. However, at 0°C the yields were relatively smaller and not very reproducible. The product obtained was a high molecular weight polymer, insoluble in most solvents, and partially crystalline. The polymerization in THF at ?20° gave 58% conversion in 9 hours with a high rate first, then a slower rate. The polymer samples were characterized by fractionation, FT-IR, DSC, NMR, TGA, and X-ray powder diffraction. The polymer samples in the solution polymerization contained trimer and oligomeric components. No glass transition temperature was observed at the temperature interval studied.