H2O/TiCl4/ED 体系引发异丁烯控制正离子聚合中的影响因素研究

在亲核试剂(ED)如吡啶(Py)、N,N-二甲基乙酰胺(DMA)或三乙胺(TEA)存在下,由引发剂H2O和共引发剂TiCl4组成引发体系,在二氯甲烷/正己烷混合溶剂中进行异丁烯(IB)正离子聚合,考察了溶剂极性、聚合温度及异丁烯浓度对聚合反应转化率、产物分子量和分子量分布的影响.试验结果表明,随聚合体系溶剂极性增大,聚合速率加快,相近转化率时聚合产物的分子量分布变窄.随着聚合温度降低,聚合速率明显提高,聚合物的分子量增加,活化能为负值,活性链端发生链转移或链终止等副反应的几率减小,当聚合温度为-60℃时,可以抑制活性链端的β-H脱除反应和链转移副反应,并得到大分子链末端全部为叔氯基团的聚异丁烯(PIB).当[IB]0≤2.5mol/L时,随[IB]0增加,聚合转化率有所增加,聚合产物的GPC谱图均为单峰分布,分子量增大,而分子量分布基本保持不变,对于加入Py的聚合体系,分子量分布指数在1.33~1.45范围内,对于加入TEA的聚合体系,分子量分布指数在1.47~1.60范围内,并求出在加入Py和TEA的聚合体系中活性链向单体的链转移常数CM分别为5.5×10-4和6.6×10-4.     

Synthesis and characterization of star-comb styrene/butadiene copolymer

<正>A novel star-comb styrene/butadiene copolymer(SC-SBC) was synthesized by anionic polymerization and grafting reaction with epoxidized star liquid polybutadiene(ESPB) as coupling agent.The overall shape of the star-comb macromolecules can be altered by changing the molecular weight and number of the side chain.The molecular parameters and mechanical properties of the SC-SBC resins were investigated.The notched izod impact strength of the SC-SBC resins are excellent and reach as high as to 239 J/m.     

机理转移法合成星形梳状聚丁二烯-g-聚甲基丙烯酸甲酯共聚物的研究

结合活性负离子聚合与原子转移自由基聚合(ATRP),采用机理转移法制备了一系列窄分布且分子量可控的星形梳状聚丁二烯-g-聚甲基丙烯酸甲酯接枝共聚物(SC-(PB-g-PMMA)).首先通过阴离子聚合,制备星形聚丁二烯,后经甲酸-过氧化氢原位环氧化对链中部分双键进行环氧化,再与原位生成2-溴异丁酸发生酯化反应,得到具有链中活性溴的星形大分子引发剂(SPB-Brn).然后,利用该大分子引发剂,采用CuCl/CuCl2/PMDETA催化体系,通过ATRP聚合单体MMA,合成出星形梳状SC-(PB-g-PMMA)聚合物.通过GPC,1H-NMR和FTIR等分析手段对合成的星形大分子引发剂及星形梳状聚合物进结构表征,证实得到目标产物,并同时研究了聚合物的热力学性质与溶液性质.     

Synthesis of well‐defined comb‐like graft (co)polymers by nucleophilic substitution reaction between living polymers and polyhalohydrocarbon

A series of graft (co)polymers were synthesized by nucleophilic substitution reaction between iodinated 1,2‐polybutadiene (PB‐I, backbone) and living polymer lithium (side chains). The coupling reaction between PB‐I and living polymers can finish within minutes at room temperature, and high conversion (up to 92%) could be obtained by effectively avoiding side reaction of dimerization when living polymers were capped with 1,1‐diphenylethylene. By virtue of living anionic polymerization, backbone length, side chain length, and side chain composition, as well as graft density, were well controlled. Tunable molecular weight of graft (co)polymers with narrow molecular weight distribution can be obtained by changing either the lengths of side chain and backbone, or the graft density. Graft copolymers could also be synthesized with side chains of multicomponent polymers, such as block polymer (polystyrene‐b‐polybutadiene) and even mixed polymers (polystyrene and polybutadiene) as hetero chains. Thus, based on living anionic polymerization, this work provides a facile way for modular synthesis of graft (co)polymers via nucleophilic substitution reaction between living polymers and polyhalohydrocarbon (PB‐I). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

丁二烯的NdCl3·2Phen-HAl(i-Bu)2催化定向聚合

本文报导了一种新的二元氯化稀土定向聚合催化剂,系由氯化钕邻菲罗啉络合物(NdCl₃·2Phen)与氢化二异丁基铝(HAl(i-Eu)₂)所组成。该体系可在较宽范围内改变聚丁二烯的分子量。本文研究了该体系作用下丁二烯聚合的一般规律,着重考察了影响产物分子量的主要因素,表明HAl(i-Bu)₂是聚合过程中的主要链转移剂,HAl(i-Bu)₂/单体比是控制产物分子量的关键变量,文内对邻菲罗啉络合分子在控制产物分子量过程中可能起的作用进行了讨论。     

超临界CO2中苯乙烯RAFT分散聚合

以末端带有三硫代碳酸酯的聚二甲基硅氧烷(PDMS-TTC)为大分子链转移剂,在超临界CO2中通过苯乙烯的可逆加成-断裂链转移(RAFT)聚合制备了聚二甲基硅氧烷-b-聚苯乙烯(PDMS-b-PS)嵌段共聚物,对聚合反应动力学以及产物的组成、分子量和形貌等进行了表征.由于PDMS链段可溶于超临界CO2而PS链段不溶,因此在超临界CO2中制备PDMS-b-PS嵌段共聚物的过程是以嵌段共聚物自身作为分散稳定剂的RAFT分散聚合,产物为粒径较均一的球形颗粒.     

枯基醇/三氟化硼在含水介质中引发苯乙烯可控正离子聚合的研究

研究了含水介质中,以枯基醇(CumOH)/三氟化硼(BF3)为引发体系的苯乙烯正离子聚合的特征,探讨了CumOH用量、体系中的水含量对苯乙烯正离子聚合转化率、聚合速率以及产物分子量及其分布的影响;并从分子模拟、分子量末端结构等角度探讨含水介质中苯乙烯正离子聚合的反应机理.结果表明,[H2O]≤0.11 mol/L条件下,苯乙烯正离子聚合具有可控聚合的特征;水对聚合速率、单体转化率以及分子量影响较小;[H2O]>0.11 mol/L,正离子聚合不能顺利进行.根据计算结果,CumOH/BF3引发体系相对于CumOH/H2O引发体系在参与引发所需要的活化能垒更小,说明CumOH/BF3更容易引发苯乙烯正离子聚合,这与实验结果一致.CumOH/BF3引发体系是通过活化C—O键来引发苯乙烯正离子聚合,水作为可逆终止剂有利于进行可控聚合,并得到了末端含有羟基的聚合物.     

丙烯酰胺基偶氮苯的RAFT聚合反应动力学

以丙烯酰胺基偶氮苯(AAAB)为单体,二硫代苯甲酸异丙苯酯(CDB)为链转移剂,偶氮二异丁腈(AIBN)为引发剂,N,N-二甲基甲酰胺(DMF)为溶剂,利用可逆加成-断裂链转移(RAFT)聚合法合成了侧链含有偶氮苯基团的聚丙烯酰胺基偶氮苯(PAAAB),同时考察了反应温度、引发剂浓度、链转移剂浓度等因素对聚合反应的影响。利用FT-IR、1H NMR、GPC等对其结构进行了表征。结果表明,聚合反应动力学曲线呈良好的线性关系,分子量分布窄;随着[CDB]/[AIBN]比例的增大,聚合速率、分子量和分子量分布均下降。     

Anionic synthesis of well-defined polymer blends by controlled chain-transfer reactions

The scope and limitations of controlled chain transfer reactions in living anionic polymerization have been investigated. In contrast to the random nature of normal chain transfer reactions, this procedure first effects controlled living anionic polymerization followed by addition of a stoichiometric amount of suitable chain transfer agent when the monomer has been completely consumed. The resulting anionic species is then used to initiated polymerization of a second monomer charge with the same monomer or with a different monomer. A variety of hydrocarbon acids and amine compounds with pKa values in the range of 30–40 have been evaluated as chain transfer agents in the presence and absence of coordinating ligands. Efficient chain transfer to poly(styryl)lithium has been observed using 1,1-diphenylpropane. Reinitiation efficiency to both styrene and butadiene monomer was quantitative and controlled blends of different molecular weight polystyrenes or blends of polystyrene with polybutadiene have been prepared. The use of these chain transfer reactions to prepare functionalized polymers has also been investigated.     

Matrix‐grafted multiwalled carbon nanotubes/poly(methyl methacrylate) nanocomposites synthesized by in situ RAFT polymerization: A kinetic study

A new approach was developed to functionalize multiwalled carbon nanotubes (MWCNTs) with a polymerizable methyl methacrylate (MMA) groups, and the structure of functionalized MWCNTs were characterized by FTIR, Raman, XPS, and TEM. Using the strategy of “grafting through,” poly(methyl methacrylate) (PMMA) chains were grafted onto the surface of MWCNTs during the in situ synthesis of MWCNT/PMMA nanocomposites over reversible addition‐fragmentation chain transfer (RAFT) polymerization. Kinetics of RAFT‐mediated polymerization of MMA in the presence of MMA‐grafted MWCNTs was studied by using gas chromatography and gel permeation chromatography. To further study, attached polymers were detached and their molecular characteristics were compared to freely formed chains. Results of kinetic studies showed that the utilized commercial chain transfer agent strictly reduced the rate of polymerization as well as relatively controlled molecular weights and narrow molecular weight distributions of free chains. MWCNTs showed a radical activity, retarding the polymerization and reducing the rate of reaction. The effect of MWCNTs concentrations on molecular weights and polydispersity indexes (PDI) was different at the surface and in the bulk. The molecular weights of free chains increased, and the PDI was decreased with increasing MWCNTs. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 555–569, 2012     

吡啶类试剂调节H_2O/TiCl_4引发苯乙烯正离子聚合研究

1988年,Kennedy等[1~3]首先实现了由BCl3共引发的苯乙烯(St)及其衍生物活性正离子聚合,但所得到聚合产物的分子量分布宽(Mw/Mn=5~6).苯乙烯活性正离子聚合的共引发剂由BCl3扩展到SnCl4、TiCl4[4~7]和TiCl3(OiPr).对于TiCl4共引发的St活性正离子聚合,所用引发剂为2,4,4-三甲基-2     

甲基丙烯酸甲酯聚合动力学和分子量及分布的开放控制

在甲基丙烯酸甲酯聚合过程中 ,凝胶效应会导致转化率在短时间内出现突变 ,这对工业反应器非常危险 ,同时也导致分子量剧增、分子量分布加宽 .为了使聚合反应速度、分子量及分布同时得到控制 ,提出 3个控制目标 ,即热荷分布指数、预定分子量及变化、分子量分布指数 .在甲基丙烯酸甲酯半间歇聚合动力学和分子量模型的基础上 ,通过单体、溶剂和链转移剂 3种物料的流量和加料方式的仿真计算 ,对动力学、分子量及分布进行开放控制 ,并进行优化 ,得到热荷分布指数和分子量分布指数分别小于 2 0和 2 2的控制策略 ,且分子量达到预定要求 .选择两种优化策略进行实验验证 ,结果与开放控制仿真结果一致     

Emulsion polymerization of styrene using irreversible addition–fragmentation chain transfer agents: effect on the course of the polymerization and molecular weight

The emulsion polymerization of styrene with three different chain transfer agents (CTAs) based on irreversible addition–fragmentation chain transfer (AFCT) mechanism was first reported in this work. The influences of these irreversible AFCT agents on the rate of polymerization, particle size, and molecular weight were investigated. It was found that the intrinsic activity and desorption behaviors of the CTAs determined the efficiency for molecular weight control, rate of polymerization, and particle size in the emulsion polymerization. It has been demonstrated that the rate of polymerization and particle size decreased dramatically in the presence of the irreversible AFCT agents with high chain transfer constant (ethyl α-p-toluenesulfonyl-methacrylate), meanwhile, the molecular weight of the polystyrene could not be controlled well, whereas the irreversible AFCT agents with low chain transfer constant (butyl(2-phenylallyl)sulfane and 2,3-dichloropropene) had a slight effect on the polymerization rate, particle size, and were fairly well for molecular weight control over the whole conversion range in the emulsion polymerization of styrene. The average number of radicals per particle and the number-average molecular weight were calculated by classical radical emulsion polymerization theory, and the experimental results were in good agreement with the results of model calculations, when the irreversible AFCT agents were used as CTAs. The effect of chain transfer agents on the kinetics and nucleation in the emulsion polymerization of styrene can be attributed to desorption of chain-transferred radicals from the polymer particles. The results of this work show that butyl(2-phenylallyl)sulfane as CTA in emulsion polymerization of styrene provides the best balance between the rate of polymerization and the efficiency for molecular weight control conflicting tendencies.     

Anionic polymerization of styrenic macromonomers of polyisoprene,polybutadiene, and polystyrene

Anionic polymerization and high‐vacuum techniques were used to prepare a series of well‐defined polyisoprene, polybutadiene, and polystyrene polymacromonomers. The procedure involved (1) the synthesis of styrenic macromonomers in benzene by the selective reaction of the corresponding macroanion with the chlorine of 4‐(chlorodimethylsilyl)styrene (CDMSS) and (2) the in situ anionic polymerization of the macromonomer without previous isolation. The synthesis of the macromonomers [polyisoprene macromonomer: 11 samples, weight‐average molecular weight (M_w) = 1000–18,000; polybutadiene macromonomer: 5 samples, M_w = 2000–4000; and polystyrene macromonomer: 2 samples, M_w = 1300 and 3600] was monitored by size exclusion chromatography with refractive index/ultraviolet detectors. Selectivity studies with CDMSS indicated that polybutadienyllithum had the highest selectivity, and polystryryllithium the lowest. From kinetic studies it was concluded that the polymerization half‐life times were longer but comparable to those of styrene, and they appeared to only slightly depend on the molecular weight of the macromonomer chain (at least for low degrees of polymerization of the polymacromonomer and for M_w < 7000 for the macromonomer side chain). Dependence on the polymerization degree of the polymacromonomer product was also observed. All the prepared polymacromonomers were characterized by size exclusion chromatography with refractive index, ultraviolet and two‐angle laser light scattering detectors, and NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1038–1048, 2005     

Ni(naph)_2/A1R_3/BF_3·OEt_2/DMEA/OctOH体系催化丁二烯配位聚合

在Ni(naph)2-AlR3-(BF3·OEt2)催化体系(简称Ni-Al-B)用于丁二烯(Bd)/己烷进行配位聚合体系中引入N,N-二甲基乙醇胺(DMEA)和辛醇(OctOH),研究了DMEA/Ni摩尔比、B/Ni摩尔比和Al/Ni摩尔比对Bd聚合转化率、聚丁二烯(PB)产物的特性黏数、分子量、分子量分布及微观结构的影响,进一步探讨聚合反应动力学.结果表明,在镍系催化丁二烯聚合体系中引入一定量的DMEA和OctOH后,可以提高顺-1,4微观结构含量至97.8%,降低1,2-微观结构含量至约1.3%,提高分子量,使分子量分布变窄,并降低凝胶含量.进一步通过调节B/Ni及Al/Ni摩尔比值,可得到[η]为2.0～4.0dL/g的高顺式PB.聚合速率对单体浓度呈现一级动力学关系,表观增长活化能为43.7kJ·mol-1。     

Viscosity effects in cobaloxime‐mediated catalytic chain‐transfer polymerization of methacrylates

The effect of bulk viscosity on the cobaloxime‐mediated catalytic chain‐transfer polymerization of methacrylates at 60 °C was investigated by both the addition of high molecular weight poly(methyl methacrylate) to methyl methacrylate polymerization and the dilution of benzyl methacrylate polymerization by toluene. The results indicate that the bulk viscosity is not directly linked to the chain‐transfer activity. The previously measured relationship between chain‐transfer‐rate coefficient and monomer viscosity therefore probably reflects changes at the molecular level. However, the results in this article do not necessarily disprove a diffusion‐controlled reaction rate because cobaloxime diffusion is expected to scale with the monomer friction coefficient rather than bulk viscosity. Considering the published data, to date we are not able to distinguish between a diffusion‐controlled reaction rate or a mechanism directly affected by the methacrylate substituent. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 782–792, 2002; DOI 10.1002/pola.10152     

Synthesis and characterization of amino-terminated telechelic polybutadiene

Butadiene was polymerized with water-soluble 4,4′-azobis(amidinopropane)dihydrochloride initiator in an ethanol-water medium at 60°C. Important variables, such as the initiator concentration, monomer concentration, solvency, and polymerization time and temperature were studied. ¹³C-NMR studies showed that no observable chain transfer to ethanol occurred during the polymerization. The conversion of monomer to polymer was significantly increased while maintaining a relatively narrow molecular weight distribution by intermittent feed of the initiator. The amidino end-groups of the polymer were transformed into amino groups by reduction using lithium aluminum hydride in THF, so that amine-terminated polybutadiene was obtained. The amino functionality of the polybutadiene was determined by titration to be 2.0. © 1995 John Wiley & Sons, Inc.     

卟啉铝催化下二氧化碳与氧化环己烯共聚反应研究

利用四苯基卟啉氯化铝(TPPAlCl)与双三苯基膦氯化铵(PPNCl)组成的二元催化剂催化二氧化碳与氧化环己烯共聚合,80℃下反应9h,二氧化碳-氧化环己烯共聚物(PCHC)的收率为97.2％,分子量分布窄(Mw/Mn=1.12),但数均分子量仅为6.8×103.研究发现溶剂的浓度和极性变化对聚合过程中的链转移反应影响...     

Iron‐mediated atom transfer radical polymerization of styrene with tris(3,6‐dioxaheptyl) amine as a ligand

The atom transfer radical bulk polymerization of styrene with FeX₂ (X = Br or Cl)/tris(3,6‐dioxaheptyl) amine as the catalyst system was successfully implemented at 110 °C. The number‐average molecular weight of the polymers with a narrow molecular weight distribution (weight‐average molecular weight/number‐average molecular weight = 1.2–1.5) increased linearly with the monomer conversion and matched the predicted molecular weight. The polymerization rate, initiation efficiency, and molecular weight distribution were influenced by the selection of the initiator and iron halide. The high functionality of the halide end group in the obtained polymers was confirmed by both ¹H NMR and a chain‐extension reaction. Because of its water solubility, the iron complexes could be removed easily from the reaction mixture through the washing of the polymerization mixture with water. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 483–489, 2006     

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.