二茚基稀土胺化物催化甲基丙烯酸甲酯聚合

传统甲基丙烯酸甲酯(MMA)立体规整性聚合,通常采用阴离子引发剂(如RMgX)在低温下进行,具有引发剂浓度高,分子量低等缺点.近年,Yasuda[1]报道了单组分茂稀土催化剂(如[(C5Me5)2SmH]2,(C5Me5)2Ln(μ-Me)2AlMe2(Ln=Yb,Y,Lu))催化MMA聚合,获得高分子量间同含量达90%以上的PMMA-(s-PMMA).而Marks[2]则报道用单组分茂稀土催化剂Me2Si(Me4C5)(RC5H3)LaN(TMS)2(R=neomenthyl)获得全同含量达90%以上的PMMA(i-PMMA).最近,我们[3]报道用单组分茂稀土催化剂(C9H7)2Y(μ-Et)2AlEt2获得高全同含量及超高分子量的PMMA.本文研究了…     

稀土催化聚合最新进展

随着聚合用稀土催化剂本质的深入研究,不断出现新的催化剂和聚合物,其中一些催化剂已实现工业比生产.本文以稀土催化剂在烯烃、双烯烃和其它单体的聚合物领域中较为突出的主要成就为中心,扼要地介绍稀土催化剂在高分子科学和工业上的最新进展.     

单组分稀土聚合催化剂研究进展

对７７篇代表性文献综述了单组分稀土聚合催化剂的最新进展,重点介绍这一催化剂的主要特征,并指出了有待解决的几个问题。     

稀土催化四氢呋喃开环聚合

1937年Meerwein首次发现Et_3O~(+BF)可催化四氢呋喃(THF)开环聚合。到目前为止,发现能使THF开环聚合的催化剂有质子酸、Lewis酸、洋离子、正碳离子等。1990年吴健等将(Acac)_3Nd-(i-Bu)_3Al-H_2O-环氧氯丙烷催化体系应用于THF聚合,发现它和(i-Bu)_3Al-H_2O-环氧氯丙烷体系具有相同的活性,这说明稀土配合物没有参与活性中心的形成。本工作发现(CF_3CO-2)3Ln(Ln=Y,La,Ce,     

烯烃聚合单组分稀土催化剂

概述了烯烃聚合单组分稀土催化剂在烯烃均聚、烯烃与烯烃、苯乙烯共聚及烯烃与极性单体共聚等研究领域的最新进展。     

载体中元素电负性对稀土催化剂聚合活性的影响

载体稀土催化剂;丁二烯聚合;载体中元素电负性对稀土催化剂聚合活性的影响     

丁二烯气相聚合的负载型稀土催化剂研究

合成了负载型稀土催化剂,并将其用于丁二烯气相聚合.研究表明,硅胶负载Nd(naph)₃-Al(i-Bu)₃-Al(i-Bu)₂Cl催化体系具有相当高的催化活性和立体定向性,其最佳组成:n(Al)/n(Nd)=40～60,n(Cl)/n(Nd)=3～7.添加适量单体丁二烯或异戊二烯,尤其是添加丁二烯,可成倍提高催化活性,随着聚合反应的进行,其速率在10min内迅速增加并达到峰值,随后降低,动力学行为属衰减型.所得聚丁二烯的分子量在几十万至百万,凝胶含量小于6%,顺-1,4结构含量达到98%左右.     

稀土催化双烯聚合研究的近期进展

稀土催化双烯聚合研究的近期进展杨继华，欧阳均（中国科学院长春应用化学研究所，长春１３００２２）自七十年代以来，有关稀土催化双烯配位聚合的研究，以其发展Ｚｉｅｇｌｅｒ－Ｎａｔｔａ定向聚合理论及开发合成橡胶新品种的重大科学意义，而成为国际上高分子化学及催...     

Ln（acac）3—BuMgCl催化甲基丙烯酸甲酯聚合

开发了催化甲基丙烯酸甲酯聚合的一类新型催化剂，由稀土乙酰基丙酮配合物Ｌｎ（ａｃａｃ）３和格氏试剂ＢｕＭｇＣｌ组成．研究了不同稀土元素、催化剂陈化时间和温度、溶剂、ＣＣｌ４添加剂、聚合时间和温度的影响．结果表明，在石油醚中单体聚合转化率和聚合物相对分子质量高于芳烃和其它极性溶剂，过量ＢｕＭｇＣｌ可能起链转移作用，降低温度可提高聚合物的间同含量．     

甲基丙烯酸甲酯在环烷酸钕-三异丁基铝α,α'-联吡啶催化体系中聚合研究

自60年代以来,Ziegler型催化剂用于极性单体甲基丙烯酸甲酯(MMA)的聚合研究较多,如由钛、矾、铁等过渡金属化合物与烷基铝组成的催化剂[1～3].近年来出现了锆、稀土配位催化聚合MMA及其他丙烯酸酯的报道[4～6],这些催化剂引发MMA聚合机理相当复杂,有的为自由基型,有的则为配位阴离子型.本文报道极性单体MMA在环烷酸钕-三异丁基铝-α,α'-联吡啶体系中的聚合特征和聚合反应动力学,并初步探讨了反应机理.     

Kinetics and Mechanism of the Polymerization of Methyl Methacrylate in a Y(acac)3/n-BuMgCl System

Based on the kinetics equation proposed by T. Kagiya, the kinetic study on the polymerization of methyl methacrylate(MMA) by Y(acac)3/n-BuMgCl was carried out with a dilatometer. It was found that the rate of propagation is the first order with respect to the concentration of both active center and monomer. Thus, the equation of propagation rate can be described as Rp=Kp[c*][M]. In addition, the instantaneous chain initiation and single molecular termination were concluded for the present system. The activation energy is close to 32 kJ/mol. In the polymerization, n-BuMgCl acts not only as the cocatalyst, but also as chain transfer agent with cI=3.6×10-4.     

Organocuprates as Initiators for Methyl Methacrylate Polymerization

Abstract

Polymerizations of methyl methacrylate initiated by organocuprates in tetrahydrofuran solution have been investigated. The heterocuprate lithium n-butylcyanocuprate was found to be an effective initiator at - 78°C, and lithium di-n-butylcuprate was confirmed as an effective initiator; both species give rapid polymerization to virtually complete conversion of monomer. Polydispersities (M_w/M_n ) are about 1.5. Polymerizations have an inherent termination reaction and a low initiator efficiency. Polymerization of methyl vinyl ketone is virtually uncontrollable, and polymerizations of methyl methacrylate are inhibited by styrene.     

Isospecific Polymerization of Methyl Methacrylate by Intramolecular Rare‐Earth Metal Based Lewis Pairs†

A series of cationic rare‐earth aryloxide complexes, i.e., [LREOAr']⁺[B(C₆F₅)₄]^– (L = CH₃C(NAr)CHC(CH₃)(NCH(R)CH₂PPh₂); RE = Y, Lu; Ar' =2,6‐tBu₂‐C₆H₃, 2,6‐(PhCMe₂)₂‐4‐Me‐C₆H₂; Ar = 2,6‐iPr₂‐C₆H₃, 2,6‐(Ph₂CH)₂‐4‐iPr‐C₆H₂; R = H, CH₃, iPr, Ph), were prepared and applied to the Lewis pair polymerization of methyl methacrylate (MMA). The stereoregularity of the resulting PMMA was significantly affected by the R substituent on the pendant arm of the tridentate NNP ligand, and was found to increase with increase in the steric hindrance of R. When using a Ph group as R, the Y complex produced a highly isotactic polymer with an mm value of 95% and a T_g of 54.6 ^oC. In contrast, the steric hindrance of the Ar and Ar' groups had no effect on the tacticity of the resulting polymer, presumably because these two substituents were situated such that they pointed outward from the cyclic intermediates. Kinetics studies demonstrated that the polymerization was a first‐order process with regard to the monomer concentration prior to catalyst deactivation. End group analysis indicated that the polymerization was accompanied by two possibly competing chain‐termination side reactions that proceeded via intramolecular backbiting cyclization.     

The Polymerization of Methyl Methacrylate in the Presence of a New Homogeneous Yttrium Catalyst

Methyl methacrylate(MMA) polymerized in the presence of a new homogeneous catalyst of Y(acac)3-(i-Bu)3Al-BuLi. The effects of MMA/Y, Al/Y, Li/Y molar ratios, polymerization temperature and time are reported. The results show that a small amount of butyl lithium could greatly enhance the activity of the catalyst and the polymerization reaction could be carried out at low temperatures (-25℃-10℃) with a high conversion. 200 kg of poly(methyl methacrylate) (PMMA) with 63% syndiotacticity could be prepared by using 1 mole of yttrium.     

甲基丙烯酸甲酯立体有规聚合

简要概括了用于甲基丙烯酸甲酯立体规整性聚合的催化剂,详细综述了茂稀土催化剂催化甲基丙烯酸甲酯聚合的新进展,并预测了今后研究的发展方向。     

Microemulsion Polymerization of Methyl Methacrylate

The microemulsion polymerization of methyl methacrylate was studied. The effects of feeding modes on the structure and the properties of the obtained polymer microlatex were investigated by measuring the conversion, the transmittance and the refractive index of the latex, and by measuring the particle size, the molecular weight and the glass transition temperature (T_g) of the polymers. The results show that compared to the batch feeding mode, the semi-continuous feeding mode is more favorable to form a PMMA microlatex with a higher transmittance, a smaller particle size, a higher molecular weight and a higher T_g. And the obtained PMMA microlatex has a 30％—40％ (mass fraction) polymer content, a 0. 03 emulsifier/water weight ratio, a 0. 05 emulsifier/monomer weight ratio and a 17 nm average particle diameter, which is very important for the industrialization of the microemulsion polymerization technique.     

杯芳烃钕配合物均相体系催化丁二烯聚合

应用新型配体杯芳烃钕配合物与三异丁基铝以及添加Al(i-Bu)₂Cl为第三组分构成二元、三元均相催化体系催化丁二烯聚合.研究结果表明,对于杯[6,8]芳烃钕(C[n]Nd_xCl_y)/Al(i-Bu)₃/汽油体系,当n(Al)/n(Nd)=40～100,50℃时具有中等催化聚合活性,所制得聚丁二烯的粘均分子量为1×10⁵～2×10⁵,顺-1,4结构含量为89%左右,添加适量Al(i-Bu)₂Cl能提高催化活性.杯芳烃钕(C[n]Nd)构成的三元体系在n(Al)/n(Nd)=30,n(Cl)/n(Nd)=1～3时不同杯芳烃的活性次序为:C6>C4>C8     

Studies on the Mechanism of Methyl Methacrylate Polymerization Initiated by Volatile and Nonvolatile Products of Methyl Methacrylate Plasma

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