氧对正丁基锂引发的丁二烯负离子聚合的影响

分别研究了两种溶剂对氧的吸附和脱附作用;氧对正丁基锂的反应历程以及对由正丁基锂引发的丁二烯负离子聚合过程的影响。     

六亚甲基亚氨基锂引发的丁二烯和苯乙烯的共聚合

研究了以六亚甲基亚氨基锂为引发剂,N,N,N’,N’-四甲基乙二胺(TMEDA)为调节剂．环己烷为溶剂的丁二烯和苯乙烯的共聚合。结果表明．随着TMEDA用量的增加,聚合反应速率加快,丁二烯-苯乙烯共聚物的无规化程度提高。在相同的TMEDA用量下,聚合反应速率与用正丁基锂作引发剂时大致相等。     

用复合烷基锂引发丁二烯聚合

对以环己烷为溶剂、四氢呋喃为微观结构调节剂、复合烷基锂为引发剂的丁二烯聚合反应过程进行了研究，考察了不同引发温度、不同配比的复合烷基锂对聚合反应的影响，并与以正丁基锂为引发剂的丁二烯聚合反应过程进行了比较。     

1,1,4,4,—四苯基—1,4—二锂丁烷引发丁二烯合成三嵌段聚合物的研究

用１，１，４，４－四苯基－１，４－二锂丁烷（ＤｉＬｉ－ＴＰＢ）为引发剂，二哌啶乙烷（ＤＰＥ）为结构调节剂，环己烷为溶剂，合成了１，２－１，４－１，２立构三嵌段聚丁二烯。研究了ＤＰＥ用量和聚合温度对聚丁二烯１，２－结构的影响和两种引发体系聚合动力学行为，求得了各种反应条件下的假一级增长速率常数和表观活化能。三嵌段聚丁二烯存在两个Ｔｇ和内耗能，呈微观相分离，且分相时融体流动性最小，屈服强度最大。     

双锂引发的丁二烯阴离子聚合动力学

以齐聚异戊二烯双锂为引发剂,环已烷为溶剂,在少量四氢呋哺(THF)存在下,研究了丁二烯阴离子聚合动力学。结果表明,该体系的双锂引发活性低于同样条件下的单锂体系,但平均反应速度相近;增长反应对单体浓度为一级关系;引发剂浓度的反应级数在1/2—1/4之间,随温度增加而减小;增长反应的表现活化能Eap和频率因子Aap分别为36.95KJ/mol和3.3×10.5L~β/Mol~β·Min。     

含氮有机锂引发剂制备溶聚丁苯橡胶

用正丁基锂(n-BuLi)和六亚甲基亚胺合成含氮有机锂引发剂六亚甲基亚氨基锂(LHMI),用于引发负离子聚合。用核磁共振的方法验证了LHMI是有效的引发剂。研究了TMEDA对LHMI引发的丁苯共聚表观反应速率常数(Kp')的影响,发现当TMEDA/LHMI质量比小于1.0时,Kp'随着TMEDA用量的增加而增加。与n-BuLi体系相比,用LHMI合成的溶聚丁苯橡胶,在不损失其他物理机械性能的基础上,滚动阻力降低。     

负离子双锂引发剂体系的研究

讨论了双锂引发剂－异二烯聚合体系的缔合模型,提出了分子内缔合是双锂矣合体系的重要特点。并中模型分析了造成双锂划戊二烯聚合产物相对分子质量为双峰并有小分子拖尾现象的原因,解释了双锂引发体系较单锂引发体系聚合速度慢的实验结果。     

新型官能化多锂引发剂的合成、表征及其动力学

用二乙烯基苯(DVB)[DVB中含有乙烯基乙苯(EVB)组分]和六亚甲基亚胺合成了一种新型含氮官能化多锂引发剂,采用气相色谱法研究了该合成反应的动力学,求得了体系内各有效组分的表观增长反应速率常数,并用该引发剂引发丁二烯聚合,用质子核磁共振仪对其产物进行了表征。结果表明,各组分的表观增长反应速率常数由大到小为：p-DVB、m-DVB、异戊二烯、m-EVB、p-EVB;该引发剂中确实含有环状胺基官能团。     

多锂引发剂引发苯乙烯-丁二烯-异戊二烯的共聚反应动力学

用正丁基锂、二乙烯基苯和异戊二烯合成了可溶于非极性溶剂的多锂引发剂体系,用其制备了苯乙烯一丁二烯一异戊二烯三元共聚橡胶,研究了温度、N,N,N′、N′-四甲基乙二胺(TMEDA)／Li^ (摩尔比,下同)及引发剂浓度对其反应动力学的影响。结果表明,随着温度的升高、TMEDA用量的增加(此时TMEDA／Li^ 不大于1)、引发剂浓度的增加,各种单体的反应速率增加;在同一条件下,单体的表观增长反应速率常数由大到小依次为丁二烯、苯乙烯、异戊二烯。     

Kinetic studies on anaerobic initiated polymerization

Using a model reaction system consisting of cumene hydroperoxide, N,N-dimethyl-p-to-luidine and O-benzoic sulfimide in toluene solvent (without reactive acrylic monomer), attempts have been made to understand the initiation mechanism operating during anaerobic polymerization. In these studies, the instrumental techniques of visible spectroccopy (VS), high performance liquid chromatography (HPLC) and infrared spectroscopy (IR) were employed. Valuable kinetic data have been obtained using these three instrumental techniques. HPLC studies have shown conclusively that the N,N-dimethyl-p-toluidine (N,N-DMpT) component is significantly depleted during the initiation step of the anaerobic process. By way of contrast, the benzoic sulfimide (BS) concentration was found to be essentially unchanged during initiation. Visible spectral changes with the model anaerobic solutions indicate that the initiation mechanism may involve radical-ionic species derived from N,N-DMpT rather than free radical reactive intermediates. Increasing the acidity of the reaction solution, with addition of acetic acid, appears to accelerate the initiation rate under anaerobic conditions.     

Kinetic study of anionic polymerization of butadiene in a polar solvent

The kinetics of the propagation reaction for the polymerization of butadiene initiated by cumyl potassium in tetrahydrofuran solution at several temperatures have been studied. Kinetic data and electrolytic behaviour indicate that polybutadienyl free ions assume the whole of the propagation reaction. At 0°C, the respective rate constants for ion-pairs and free ions are 1 l mol^?1 s^?1 and 4.8 × 10⁴ l mol^?1 s^?1 respectively. The ionic dissociation constant is 7.8 × 10^?9 mol/l. The activation energy of the propagation reaction for free ions is 6.5 kcal/mol.     

Kinetic model for lonic polymerization initiated by difunctional initiator with monomer transfer

The kinetics of difunctional ionic polymerization with monomer transfer and without assumption of instantaneous initiation is studied theoretically. The set of kinetic differential equations is rigorously solved by way of graphical theory. Expressions for the molecular weight distribution (MWD) function, the number- and weight-average degrees of polymerization, and the distribution of functionality are obtained. A procedure is proposed for calculating the MWD curve and the values of other molecular parameters.     

Kinetic study of aqueous polymerization of methyl methacrylate initiated by Ce(IV)-maltose redox system

Polymerization of methyl methacrylate initiated by ceric ammonium nitrate-maltose has been investigated in aqueous nitric acid under nitrogen in the temperature range 20.5-35°C. The dependence of the initial rate of polymerization and the initial rate of ceric ion consumption on maltose, Ce(IV), and monomer concentrations has been determined. The reaction orders were found to depend on ceric ion concentration. At a moderately high Ce(IV) concentration (1 × 10^?3mol litre^?1) the orders were 1/2 and 3/2 with respect to maltose and monomer concentration, respectively, and independent of Ce(IV) concentration. But at a low Ce(IV) concentration (4 × 10^?4mol litre^?1) the orders with respect to monomer and Ce(IV) changed to 1 and 1/2, respectively. The effect of temperature was also examined. The average molecular weight, as determined by size-exclusion chromacography, was found to depend on maltose, Ce(IV), and monomer concentrations, as well as on temperature.     

Kinetic study of the polymerization of chloro ethyl vinyl ether initiated by the system hydrogen iodide/iodine

Summary A kinetic study of the cationic polymerization of chloroethyl vinyl ether initiated by the system hydrogen iodide — iodine has been performed in order to understand some particular characteristics of the system. As previously reported by Higashimura the polymerization shows a living character at low temperature in toluene. A polymerization process with a first order in iodine and 0.3 order with respect to monomer, has been observed. These results are consistent with the existence of reversible elementary processes involving iodine and monomer.Unité associée CNRS et ENSCPB     

Living/controlled hex-1-ene polymerization initiated by nickel diimine complexes activated by non-MAO cocatalysts: Kinetic and UV-vis study

Living/controlled polymerization of hex-1-ene initiated by nickel diimine catalysts of general form [ArN=C(1,8-naphthalenediyl)C=NAr]NiBr₂ activated by simple organoaluminium compounds was investigated. Polyhexenes with a very narrow molar mass distribution and molar mass controlled by the monomer/initiator ratio were prepared using diethylaluminiumchloride, ethylaluminiumdichloride and methylaluminiumdichloride as cocatalysts for nickel complexes 1 (Ar = 2,6-iPr₂C₆H₃) and 2 (Ar = 2-tBuC₆H₄). Nickel complexes with smaller aryl substituents (3, Ar = 2,6-Me₂C₆H₃; 4 Ar = 2,4,6-Me₃C₆H₂; 5, Ar = 2,6-Et₂C₆H₃) undergo transfer reactions significantly. For the most bulky complex 1 activated by ethylaluminiumdichloride living hex-1-ene polymerization was achieved, proved by the reinitiation of polymer growth upon the addition of fresh monomer. The effect of Al/Ni ratio on the activity of the catalytic systems was studied by dilatometry. The catalytic systems were investigated by UV-vis spectrometry and a new interpretation of their absorption spectra was suggested.     

Kinetic modeling of polymerization of butadiene using cobalt-based Ziegler–Natta catalyst

The reaction mechanism and subsequent kinetics for polymerization of butadiene using cobalt-based Ziegler-Natta catalysts have been investigated by many researchers. Kinetic models developed from these investigations can be used to predict the monomer conversion quite accurately; however, it is difficult to develop models that accurately predict the molecular weight as a function of time or conversion. In this paper, an attempt is made to model the reaction mechanism for the polymerization of butadiene using the cobalt octoate/diethyl aluminum chloride/water catalyst system with data taken from the literature. A dual active site mechanism is proposed and incorporated in a kinetic model. In this case, all reaction steps except the formation of byproducts step have two rate constants. The simulation results predict the molecular weight as a function of conversion and time better than results from previously published models.     

微悬浮聚合法合成聚醋酸乙烯酯的动力学研究

采用微悬浮法合成聚醋酸乙烯酯,对其聚合反应的动力学进行了研究。考察了引发剂浓度、乳化剂浓度、单体浓度以及温度对聚合反应速率的影响。结果表明,聚合反应速率对引发剂浓度、乳化剂浓度和单体浓度的反应级数分别为0．45,0．28,1．90,单体浓度对聚合反应速率的影响最大,反应体系的表观活化能为105．96 kJ/mol。     

Kinetic study of photoinitiated frontal polymerization

The frontal polymerization of a monomer exposed continuously to UV radiation in the presence of a photobleachable initiator has been studied on the basis of the rate equations. The time dependence of photoinitiator concentration profile and that of monomer conversion within the irradiated sample have been calculated, assuming steady‐state conditions. It is thus possible to visualize how fast the polymerization profile is moving within the sample and how effectively the polymerization of a monomer layer located at a given distance from the surface proceeds upon exposure to UV radiation. © 2001 Society of Chemical Industry