乙醚中异戊二烯负离子聚合动力学研究

研究了以乙醚为溶剂 ,用正丁基锂引发异戊二烯负离子聚合的动力学。结果表明 ,增长反应速率对单体浓度的反应级数为1 ,对引发剂浓度的反应级数小于1 ,说明聚合活性中心有缔合态存在 ,并未完全解缔。同时求得了增长反应速率常数、活化能、频率因子及形成1 ,4 -结构、1 ,2 -结构和3 ,4 -结构的分速率常数、分活化能和频率因子。     

异戊二烯／THF负离子聚合产物的微观结构

研究了２０～５０℃下,以ｎ－ＢｕＬｉ为引发剂,环己烷为溶剂,ＴＨＦ为极性调节剂的异戊二烯负离子聚合产物的微观结构。结果表明：随聚合温度升高,聚异戊二烯的３,４－结构含量降低;在同一温度下,随ＴＨＦ用量的增加,３,４－结构含量增加。［ＴＨＦ］／［ｎ－ＢｕＬｉ］（Ｒ,摩尔比）大于１２时,才会出现１,２－结构,且聚合温度越高,出现１,２－结构时的Ｒ值越高,并随Ｒ值的继续升高,１,２－结构含量也不断增加。此外,还建立了４个微观结构含量与ＴＨＦ用量的定量关系式。     

异戊二烯在环己烷-二氧六环中的负离子聚合机理

推导了异戊二烯在环己烷－二氧六环混合剂中的负离子聚合机理,并通过实验进行了验证。研究表明,丁二烯聚合机理原则上同样适用于异戊二烯的负离子整合,推导出非1,4－结构产物含量与极性添加剂用量的关系式为1g[(a-b)/(xv-b)-1]=nlg[PA] lgK‘,求得了a,b,n,K′与温度的关系式,并指明了各自的物理意义。     

异戊二烯在二氧六环中的负离子聚合动力学

研究了以正丁基锂为引发剂 ,异戊二烯在二氧六环溶剂中负离子聚合的动力学。结果表明 ,增长反应对单体浓度和引发剂浓度皆为一级反应 ,活化能为45.22kJ/mol,频率因子为4.832×108L/(mol·min) ,并求出了生成1,4 -结构、1,2 -结构和3,4 -结构产物的速率常数分别为2.77×1012exp( -74760/RT) ,9.82×106exp( -39190/RT) ,8.02×107exp( -41180/RT)。     

n—BuLi的浓度对异戊二烯聚合的影响

研究了不同ｎ－ＢｕＬｉ浓度时的异戊二烯假一级增长反应速率常数Ｋｐ＾″,发现当［ｎ－ＢｕＬｉ］低于７×１０＾－４ｍｏｌ／Ｌ时,Ｋｐ＾″随［ｎ－ＢｕＬｉ］的增大而增大;［ｎ－ＢｕＬｉ］高于７×１０＾－４ｍｏｌ／Ｌ时,Ｋｐ＾″随［ｎ－Ｂｕｌｉ］的增加而有所下降。［ｎ－Ｂｕｌｉ］不大于７×１０＾－４ｍｏＬ／Ｌ时的动力学方程为Ｒｐ＝０．３７［ｎ－Ｂｕｌｉ］＾０．２６６［Ｍ］。     

负离子聚合法合成丁二烯-异戊二烯无规共聚物的序列结构

以正丁基锂(n-BuLi)为引发剂、十二烷基苯磺酸钠(SDBS)为调节剂,在环己烷中对丁二烯(Bd)和异戊二烯(Ip)进行负离子聚合制得Bd-Ip共聚物,考察了反应温度、单体配比及调节体系对Ip共聚活性及共聚物序列分布的影响。结果表明,提高反应温度或增加Ip单体含量、SDBS/n-BuLi(摩尔比)由0/1.0增大到0.5/1.0,均可提高Ip共聚活性;共聚物序列分布服从一级Markov统计模型,在70℃、Ip/Bd(质量比)5/5、SDBS/n-BuLi(摩尔比)0.5/1.0、单体质量浓度0.12 g/mL的条件下,在共聚物中Ip、Bd 2种单元的同等长度单元组浓度趋于一致,所得共聚物的无规化程度高。     

在二硫化碳/正丁基锂/环己烷体系中合成高顺式聚异戊二烯

研究了聚合温度在30～60℃,以正丁基锂为引发剂、环己烷为溶剂、二硫化碳为结构调节剂的异戊二烯负离子聚合的反应规律,以及二硫化碳用量和聚合条件对聚异戊二烯微观结构的影响。结果表明,随着异戊二烯/环己烷的增加,聚异戊二烯中的顺式-1,4-结构含量降低;随着引发剂浓度的增加,顺式-1,4-结构含量也降低;随着反应温度升高,顺式-1,4-结构含量先增加后降低;随着二硫化碳用量的增加,顺式-1,4-结构含量先增加后略有降低。在50℃、异戊二烯/环己烷(质量比)为1/9、正丁基锂/异戊二烯(摩尔比)为0.68×10-3及二硫化碳/正丁基锂(摩尔比)为0.08×10-3时可制得顺式-1,4-结构摩尔分数最高约为96%的高顺式聚异戊二烯。     

负离子双锂引发剂体系的研究Ⅱ.双锂引发剂-异戊二烯聚合体系的缔合

讨论了双锂引发剂－异戊二烯聚合体系的缔合模型,提出了分子内缔合是双锂引发剂聚合体系的重要特点。并用这种模型分析了造成双锂引发异戊二烯聚合产物相对分子质量分布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     

以邻甲基苯酚钾为助引发剂的异戊二烯负离子调节聚合

采用邻甲基苯酚钾(o-ROK)为助引发剂,研究了正丁基锂(n-BuLi)/o-ROK/2G/异戊二烯/二甲苯聚合体系的聚合规律.结果表明,加入o-ROK对异戊二烯转化率影响不大;o-ROK/Li(摩尔比,下同)从0增加到0.5时,链转移数(Nt)迅速增大;当o-ROK/Li大于1.0时,M变化缓慢;聚合物的1,2-结构和3,4-结构摩尔分数随o-ROK/Li的增大而减少,1,4-结构的摩尔分数则升高.当o-ROK/Li大于0.5时,曲线的变化趋势变缓.这表明体系中活性种PLi·2G络合体的调节结构能力大于PK,PLi以及它们的缔合体等活性种.     

DDS对锂系异戊二烯聚合反应的影响研究

研究了以正丁基锂为引发剂、环己烷为溶剂、在异戊二烯阴离子聚合过程中,二苯基二甲氧基硅烷（DDs）作为添加剂对聚合反应的影响。实验结果表明：DDS可提高催化剂活性,可调节聚合物的顺l,4-结构的含量,顺式1,4-结构的质量分数达86％以上。     

Cationic polymerization of isoprene using zinc halides as co‐initiators: towards well‐defined oligo(isoprene)s under mild conditions

The activity of ZnX₂‐based initiating systems (X = Cl, Br, I) in the cationic polymerization of isoprene was studied. The highest activity was achieved when co‐initiator (ZnX₂) was solubilized in a minimal amount of strongly coordinating solvent such as diethyl ether or acetone and when trichloroacetic acid was used as an initiator. It is shown that the polymerization rate increased in the series ZnI₂ < ZnCl₂ < ZnBr₂. An increase of initiator concentration and temperature also led to an increase of the polymerization rate. The obtained polyisoprenes did not contain high‐molecular‐weight and insoluble fractions and were characterized by low number‐average molecular weight and relatively narrow molecular weight distribution. Unsaturation of polyisoprene decreased with an increase of monomer conversion and reaction temperature. The unsaturated part of the polyisoprene chain possessed predominantly 1,4‐trans microstructure with regular and inverse addition, whereas the 1,2‐ and 3,4‐isomers were present as minor components. It is shown that the synthesized low‐molecular‐weight polyisoprenes are effective plasticizers for rubber compounds in the manufacture of tyres. © 2012 Society of Chemical Industry     

Classification of polar additives with respect to their influence on the microstructure in anionic polymerization of isoprene with butyllithium by transition energy measurements

A transition energy scale was established on the basis of dimethyl indoaniline as organic dye for 23 mono- and bidentate polar additives. From polymerization experiments of isoprene with s-butyllithium in mixtures of n-hexane and the selected bases, the microstructure of polyisoprenes was determined by ¹H-NMR spectroscopy. The vinyl contents of these polymers could be satisfactorily correlated with the transition energy measurements. However, it turned out that especially bidentate bases do not fit into this scheme. Obviously, besides their influence on the polarity of the reaction solution, they exhibit special interactions with the growing centers. The developed correlations allow the prediction of 1,2- and 3,4-linkages in polyisoprenes from anionic polymerization of isoprene with butyllithium in polar solvents in the presence of low concentrations, also of bases hitherto not investigated. The temperature dependence of the microstructure can likewise be estimated. As in the case of butadiene, at least for weak bases, it was found that the vinyl contents depend primarily on the polarity of the reaction mixture determined by the base concentration and not on the molar ratio of base to initiator. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1533–1547, 1999     

Effects of amines on the polymerization of isoprene with sec-butyllithium catalyst

Polymerization of isoprene (IP) with alkyllithium (RLi) catalysts in the presence of amines such as triethylamine (TEA), 1,2-dipiperidinoethane (DPPE) and N,N,N′,N′-tetramethyldiaminoalkanes [(CH₃)₂N(CH₂)_nN(CH₃)₂ where n=1, 2, 3, 4 and 6 (TMDAA)] has been studied. By adding the amines, the polymerization rate of IP was accelerated, and the contents of 3,4- and 1,2-units in the resulting polymers increased. The effects of methylene chain length of the TMDAA on the polymerization were examined. It was found that both the polymerization rates and the microstructure of the polymers depend on the methylene length of the TMDAA. The amines having 2 and 3 methylenes in (CH₃)₂N(CH₂)_nN(CH₃)₂ favoured production of the polymer consisting of predominantly 1,2- and 3,4-units. It was proposed that two types of active sites for the polymerization of IP were produced depending on the number n of the TMDAA. Two types of active species were confirmed to be produced with sec-BuLi in the presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA) depending on the TMEDA/sec-BuLi mole ratios. © 1998 SCI.     

以亚磷酸二乙酯为第三组分的铁系催化体系催化异戊二烯聚合

以乙酰丙酮铁(简称Fe)/三异丁基铝(简称Al)/亚磷酸二烷基酯(简称DP)为催化体系,对异戊二烯进行聚合,考察了不同DP(烷基为甲基、乙基、正丁基或异辛基)、催化剂组成及反应条件对聚合的影响。结果表明,以亚磷酸二乙酯(DEP)为第三组分的催化体系,在己烷中于相对较高温度(50℃)下的催化活性最高。催化剂最佳配比为Al/Fe(摩尔比)15,DEP/Fe(摩尔比)2．0。所得聚异戊二烯橡胶的3,4-结构(含1,2-结构)摩尔分数约为60％,微观结构基本不受反应条件的影响。     

结构调节剂对液体异戊二烯聚合的影响

采用锂系阴离子聚合工艺合成液体异戊二烯橡胶( LIR),在聚合过程中添加5种不同的结构调节剂,研究他们对LIR结构的影响。结果表明：非极性调节剂二硫化碳(CS₂)对LIR顺-1,4含量的影响不大;极性调节剂均可降低顺-1,4含量。其中二乙二醇二甲醚(2G)、四甲基乙二胺(TMEDA)对顺-1,4含量的调节作用较大;乙醚(Et₂O)对顺-1,4含量的调节作用较小;四氢呋喃(THF)作为结构调节剂效果最好。