Anionic Polymerization and Copolymerization of Hydrocarbon Monomers Catalyzed by Organobarium Initiators

The barium salt of the dimeric dianion of 1,1-diphenylethylene (Ba-DPhE) initiates polymerization and copolymerization of monomers capable of anionic polymerization (butadiene, isoprene, styrene) in ethereal and hydrocarbon solvents. Ba-DPhE is more stereospecific in butadiene polymerization (up to 70% of cis-1, 4-units in hydrocarbon medium) than initiators based on other metals of Groups I and II. The relative reactivity of monomers in copolymerization processes in THF decreases in an order typical for anionic polymerization: styrene > butadiene > isoprene. The most interesting feature of organobarium initiators is their ability to form random butadiene-styrene copolymers with high cis-1,4-butadiene unit content when copolymerization proceeds in a hydrocarbon medium.

A new phenomenon in anionic polymerization, the dependence of diene units structure on copolymer composition, was observed. Thus an increase of styrene content in butadienestyrene copolymer leads to conversion of cis-1,4-butadiene units into trans-1,4-units (in benzene) or to conversion of 1,4-units to 1,2-units (in THF). Similarly, an increase of butadiene content in its copolymer with isoprene (in benzene) leads to conversion of cis-1,4-isoprene units into trans-1,4-units.

Spectrophotometric, conductometric, and viscometric methods were used to study organobarium active centers. Certain anomalies connected with the formation of specific aggregates due to coupling of bifunctional hydrocarbon chains with bivalent counterions were observed.     

Functional Monomers and Polymers L Post-1 rradiative Polymerization of Butadiene in Deoxycholic Acid Canal Complexes

The polymerization of butadiene was studied in deoxycholic acid canal complexes under various reaction conditions. To prepare the starting canal complex containing butadiene, acetone in the deoxycholic acid-acetone canal complex was replaced with butadiene effectively. Post-irradiative polymerization was carried out after irradiation with γ-rays from a Co-60 source. The polymer was found to contain a significant amount of 1,2-units in addition to trans- 1,4-units. Various additives had a marked effect on the polymerization behavior, particularly on the polymer yield and the microstructure of the polymer.     

Polymerization of isoprene with cobalt catalysts

The polymerization of isoprene with catalytic systems efficient for the cis polymerization of butadiene, i.e., cobalt 2-ethyl hexanoate-diethylaluminum chloride and cobalt 2-ethyl hexanoate-ethylaluminum sesquichloride, is studied. The catalysts are obtained via in situ mixing of the components or at a reduced temperature (0–5°C) in the presence of a small amount of the monomer. In situ polymerization proceeds with an induction period, whose duration depends on the polymerization conditions, or without this period if a preformed catalyst is used. In each case, the resulting polymer is characterized by a mixed microstructure with a predominant content of cis-1,4 units and 3,4 units.     

Polymerization of butadiene catalyzed by a cobalt-containing catalyst in aliphatic media

The polymerization of butadiene catalyzed by the preformed Co(2-ethylhexanoate)₂-Et₃Al₂Cl₃-isoprene (a molar ratio of 1: 20: 20) catalytic system in toluene, cyclohexane, and hexane has been studied. In toluene, the catalyst demonstrates high activity and stereospecificity and yields a high-molecular-mass polymer. In cyclohexane and hexane, the catalyst has a high activity but affords polymers with lower contents of 1,4-cis-units and reduced intrinsic viscosities. The addition of EtAlCl₂ and/or a decrease in the polymerization temperature make it possible to obtain polybutadiene containing more than 96% 1,4-cis-units and an acceptable intrinsic viscosity (2.0–2.8 dl/g) in the nonaromatic solvents as well.     

The nature of active sites in butadiene polymerization catalyzed by organotitanium(III) derivatives

The stereospecificity of benzyl derivatives of trivalent titanium (R_n TiX_3–n, where X = Cl, I, n = 1–3) in butadiene polymerization was studied. It was found that dibenzyltitaniumiodide is an efficient catalyst of the 1,4-cis-polymerization of butadiene and that tribenzyltitanium forms 1,2-units. In both cases all the titanium-benzyl bonds participated in the initiation reaction and the active sites were polymeric analogues of crotyl derivatives of Ti(III); namely, bis-π-oligobutadienyltitaniumiodide and tris-π-oligobutadienyltitanium. These sites are stable at room temperature. The nature of the active sites in the polymerization of butadiene with Ziegler's 1,4-stereo-specific systems Til₄ (or Til₂Cl₂) + AIR₃ are described.     

The nature of active sites and stereospecificity of their action in diene polymerization catalysed by chromium-containing systems

A study has been made of the nature of active sites, stereospecificity of their action and the regularities of diene polymerization catalysed by chromium-containing systems. All possible polymer structures with high stereospecificity can be produced for butadiene and isoprene with π-allyl chromium compounds. Tris-π-allyl chromium produces polybutadiene predominantly of 1,2-units. Cis-polybutadiene is formed when the electronegative group (Cl^?, CCl₃COO^?) is substituted for one or two π-allyl groups in Tris-allyl chromium or in the catalytic system (π-C₃H₅)₃CrAl₂O₃. A catalyst obtained through interaction of (π-C₃H₅)₃Cr with silica-alumina or silica gel produces 1,4-trans-polybutadiene and 1,4-trans-polyisoprene. The rate of butadiene polymerization in the presence of Tris-π-allyl chromium is given by k[Cr]², and in polymerization of isoprene with the catalytic system (π-C₃H₅)₃Cr-silica-alumina, by k[Cr].[M]². Polymerization of dienes catalysed by (π-C₃H₅)₃Cr-silica-alumina system or supported chromium oxide catalyst proceeds according to a type of living system. A study was made of copolymerization of butadiene and isoprene in the presence of supported chromium oxide catalyst and with that produced by the reaction of (π-C₃H₅)₃Cr with silica-alumina. The constants of copolymerization for the systems were equal. A conclusion has been drawn regarding the similar mechanisms for diene polymerization under the action of supported chromium oxide catalyst or of catalyst formed in the reaction of (π-C₃H₅)₃Cr with silica-alumina or silica gel.     

Alternate Transition Metal Complex Based Diene Polymerization

Abstract

In the last decade, there has been a tremendous increase in the number of reports on transition metal complex-mediated butadiene homo- and copolymerization. While typical classical titanium, nickel, cobalt, and neodymium based catalysts have been almost exclusively applied to the production of high cis-1,4-polybutadiene, alternative catalyst systems are currently being developed which enable tuning of the polybutadiene microstructure and permit defined changes in polymer properties such as molecular weight distribution and changes in the polymer glass temperature. Besides new products such as high trans-1,4-polybutadiene or a polymer containing a defined amount of 1,2-polybutadiene, there are butadiene copolymers with different amounts of styrene, isoprene, or ethylene. These new materials should lead to new applications especially in the area of tires, high impact polystyrene (HIPS), and ABS. This review elucidates the new developments in the area of transition metal complex-based butadiene homo- and copolymerization focusing mainly on the transition metal catalyst, the polymerization process and the resulting polymers. Mechanistic details are discussed briefly and wherever useful for the understanding of the polymerization reaction.     

聚合物载体-稀土金属络合物的表征及其催化聚合共轭双烯的活性

本文采用含一定量功能团的直链碳氢共聚物作为载体,如苯乙烯-丙烯酸共聚物(SAAC),苯乙烯-2-(甲基亚硫酰基)乙基甲基丙烯酸酯共聚物(SMC)。介绍了这类聚合物载体-稀土金属络合物的合成方法,讨论了它们的红外光谱。聚合物载体-钕络合物催化剂具有很高的催化活性和定向效应.SAAC·Nd 三元体系的催化效率高达170kg聚丁二烯/gNd·小时,SMC·NdCl_3 二元体系的催化效率是小分子氯化钕二甲基亚砜络合物 NdCl_3·4DMSO的 2—3倍。聚丁二烯顺式-1,4结构含量在 98％以上。体系也适用于异戊二烯的聚合,产物顺式-1,4含量在95％左右。     

Nature of active centers and stereospecificity of tetravalent titanium benzyl derivatives in polymerization of butadiene

Stereospecificity of tetrabenzyltitanium and its halogeno-derivatives in the polymerization of butadiene has been investigated. The content of 1,2-units decreases while the content of 1,4-cis-units increases in the resulting polybutadiene for the series (C₆H₅CH₂)₄Ti, (C₆H₅CH₂)₃TiCl, (C₆H₅CH₂)₃TiBr, (C₆H₅CH₂)₃Til. Tribenzyltitanium iodide exhibits high stereospecificity for the formation of 1,4-cis-units and their content reaches 94–97%. By determining the number of benzyl groups linked with titanium at different degrees of conversion, it has been shown that the active centre formed from tetrabenzyltitanium contains three benzyl groups and one polymer chain. Two benzyl groups, one iodine atom and one polymer chain are attached to a titanium atom in the active centre for the case of tribenzyltitanium iodide. Electron donors sharply change the stereospecificity of tribenzyltitanium iodide: the content of 1,2-units in the polymer rises to 68%.     

Active centre structure and the stereoregulation process in anionic polymerization

The mechanism of stereoregulation in the anionic polymerization of butadiene and isoprene is discussed in terms of what is known about the structure of the active centres. This includes the effect of the presence of cis and trans isomers and the dynamics of their interconversion and in the isoprene case, the effect of two distinct types having 1,4 and 4,1 structures.     

Molecular structure of polybutadienes synthesized with a lithium-containing initiation system

With the use of high-resolution NMR spectroscopy (600 MHz) and gel-permeation chromatography, the products of anionic polymerization of butadiene initiated by n-butyllithium modified with sodium and magnesium alcoholates are studied. It is shown that a change in synthesis conditions makes it possible to vary the configuration and isomeric composition and molecular parameters of polybutadienes. The distribution of 1,2-, cis-1,4-, and trans-1,4-units in a chain has a pronounced statistical character and depends on the composition of the initiation system.     

Polymerization of butadiene with titanium-magnesium nanocatalysts

The suspension polymerization of butadiene in the presence of titanium-magnesium nanocatalysts combined with triisobutylaluminum is studied. The resulting polybutadiene is shown to contain up to 99% trans-1,4-units. The dependences of polymer microstructure on temperature and the Al-to-Ti ratio are investigated. The kinetic parameters of the process and the properties of trans-1,4-polybutadiene are examined.     

Synthesis of hydroxyl-terminated polybutadiene possessing high content of 1,4-units via anionic polymerization

<正>The hydroxyl-terminated polybutadiene(HTPB) possessing high content of 1,4-units was synthesized by anionic polymerization of butadiene,using alkyllithium containing silicon-protected hydroxyl group as initiator and cyclohexane as solvent.The polymers were characterized by GPC,IR and ~1H-NMR.The mechanical properties of cured films were also evaluated.The results show that the content of 1,4-units for HTPBs made by anionic polymerization reaches up to 90%.The molecular weight distribution is very narrow(≤1.05).The functionality of hydroxyl groups approaches 2.Compared with free radical HTPB,the elongation at break of anionic HTPB films increased by 70%,while the tensile strength remained nearly unchanged.This new HTPB can be very useful in solid propellant.     

Inclusion polymerization of various diene monomers in apocholic acid canals

The inclusion polymerization of diene monomers with different sizes and shapes in apocholic acid canals was studied under -ray irradiation. It was found that the sizes and shapes of monomers profoundly influenced the microstructures of the corresponding polymers obtaied. Thus, polybutadiene contained a significant amount of 1,2-units like usual radical polymerization in solution. Polyisoprene consisted of a mixture of head-to-tail and head-to-head (tail-to-tail) addition. The introduction of two methyl groups into butadiene led to the synthesis of polymers with almost exclusively head-to-tail, 1,4-trans structure.     

Characterization of Polymer-Supported Rare-Earth Metal Complexes and Their Catalytic Behavior in Polymerization of Conjugated Dienes

The polymerization and catalytic behavior of catalyst systems composed of polymer-supported rare-earth metals were investigated. The catalyst systems show high catalytic activity and stereospecificity for butadiene polymerization. The catalytic efficiency for SMC (styrene-2-(methylsul-finyl)ethyl methacrylate copolymer).NdCl_3-Al(i-C₄H₉)₃ system is twice or three times that of the NdCl₃.4DMSO system. The activity of the ternary system SAAC (styrene-acrylic acid copolymer).Nd-Ph₃CCl-Al(i-C₄H₉)₃ was up to 170 kg polybutadiene/(g Nd-h). The cis-1,4 content of polybutadiene was more than 98%. This system was also used for isoprene polymerization. The cis-1,4 content of the polyisoprene obtained was about 96%     

Copolymerization of 1,3‐butadiene and isoprene with cobalt dichloride/methylaluminoxane in the presence of triphenylphosphine

The homopolymerization and copolymerization of 1,3‐butadiene and isoprene were achieved at 0 °C with cobalt dichloride in combination with methylaluminoxane and triphenylphosphine (Ph₃P). For 1,3‐butadiene, highly cis‐specific and 1,2‐syndiospecific polymerization proceeded in the absence or presence of Ph₃P, respectively, although the activity with Ph₃P was much higher than that without Ph₃P. Only a trace of the polymer was, however, obtained in isoprene polymerization when Ph₃P had been added. For copolymerization, the polymer yield in the presence of Ph₃P was about three times higher than that in its absence. Copolymerization in the presence of Ph₃P was, therefore, investigated in more detail. Unimodal gel permeation chromatography elution curves with narrower polydispersity (weight‐average molecular weight/number‐average molecular weight ≈ 1.5) indicated that the propagation reaction proceeded by single‐site active species. Both the yield and molecular weight of the copolymer decreased with an increasing amount of isoprene in the feed, and this was followed by an increase in the isoprene content in the copolymer. The monomer reactivity ratios, r₁ (1,3‐butadiene) and r₂ (isoprene), were estimated to be 2.8 and 0.15, respectively. Although the 1,3‐butadiene content in the copolymer was strongly dependent on the comonomer composition in the feed, the ratio of 1,2‐inserted units to 1,4‐inserted units of 1,3‐butadiene was constant. Concerning the isoprene unit, the percentage of 1,2‐ and 3,4‐inserted units was increased at the expense of 1,4‐inserted units with an increasing isoprene content in the feed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3086–3092, 2002     

Metal-containing initiator systems. VI. Polymerization of butadiene with metal–organic halide systems

The polymerization of butadiene with binary initiator systems consisting of some activated metals and organic halides was investigated at 60°C. From the results obtained, it was found that systems of reduced nickel and methyltrichlorosilane or dimethyldichlorosilane were most effective for the polymerization, and those of reduced nickel and carbon tetrachloride, benzyl chloride, benzyl bromide and benzoyl chloride, showed moderate activity. The polybutadienes obtained with these systems were observed to contain product of more than 80% cis-1,4 microstructure. From detailed studies on the reduced nickel–methyltrichlorosilane system, these polymerization mechanisms were explained by the hypothesis that the initiation occurred through the reaction of the dissociated transition state complex with the monomer or with a trace amount of water, and then the propagation proceeded via a coordinated cationic mechanism. These systems did not show a good activity for the cis-1,4 polymerization of isoprene.     

Localization of Failures in Structural Order of <Emphasis Type="Italic">trans</Emphasis>-1,4-Butadiene Units in Interdefective Regions of a Butadiene-Nitrile Elastomer Matrix

The fractional free volume of chains passing and incorporated into the ordered structures of segments in trans-1,4-configuration in the copolymers of butadiene and acrylonitrile at different content of acrylonitrile units is calculated in order to determine the localization of order disturbances of butadiene trans-1,4-units. Amorphization of the structure occurs in the immediate vicinity of structural defects of acrylonitrilebutadiene rubbers formed by alternating acrylonitrile and trans-1,4-units of butadiene as well as cis-1,4-and 1,2-isomers of butadiene.     

结晶3,4-聚异戊二烯的合成

<正> 非结晶的3,4-聚异戊二烯的合成已有一些报道,本文则采用合铁的三元催化体系:三乙酰基丙酮铁-含氮给电子试剂-三异丁基铝,可使异成二烯聚合得到高3,4-链节含量,高分子量以及高熔点的结晶聚合物。 1.试剂及聚合反应 异戊二烯为聚合级产品,用前经常压蒸馏除去阻聚剂后,用活性氧化铝浸泡48小时     

A STUDY OF POLYBUTADIENE SYNTHESIS WITH MoCl_n(OR)_(4-n)-(i-Bu)_2AlOPh AS A CATALYST

The catalytic effect of Mo Cl_n (OR)_(4_n)-(i-Bu)_2AlOPh on the polymerization of butadiene inhydrogenated gasoline is studied (R is alkyl, cycloheptyl, phenyl of C_(4_16)). In this system, the solu-bility and the catalytic activity of the catalyst do not depend on whether the number of carbon atomsin R group is odd or even. The R group with the primary and secondary carbon atom has a fairlygreat influence on the catalytic activity. When R is an alkyl, the catalytic activity increases and therange of Al/Mo values that keeps higher conversion of butadiene is broadened as the size of the Rgroup increases. The content of 1,2-units in the polymer hardly varies with the size of the R group.