5 Polymeric Dienes Walter Kaminsky and B. Hinrichs University of Hamburg, Hamburg, Germany I. INTRODUCTION Homopolymers of conjugated dienes such as 1,3-butadiene, isoprene, chloroprene, and other alkylsubstituted 1,3-butadienes, as well as copolymerzs with styrene and acrylonitrile, are of great economical importance [1–3]. The conjugated dienes can polymerize via 1,4 or 1,2 linkage of monomeric units. In addition to this, 3,4 linkage occurs with butadienes bearing substituents in the 2-position. In the case of 1,4 linkage the polymer chain can exist as cis or trans type: ð1À3Þ 1,2 Linkage yields a tertiary carbon atom, thereby making it possible to form isotactic, syndiotactic, and atactic polybutadiene (3), in analogy to polypropene. The rare 3,4 linkage also gives isotactic, syndiotactic, or atactic configuration. This applies only to high stereoselectivities. Further isomeric structures are formed when next to head-to-tail linkages; head-to-head and tail-to-tail linkages also occur. The polymerization of dienes can be initiated ionically by coordination catalysts or by radicals [4–10]. Copyright 2005 by Marcel Dekker. All Rights Reserved. II. POLYBUTADIENE Polybutadiene belongs to the most important rubbers for technical purposes. In 1999 more that 2 million tons were produced worldwide, that is about 20% of all synthetic rubbers [11,12]. The cis type made by 1,4-addition is economically the most important polybutadiene [13,14]. Trans- as well as isotactic, syndiotactic, or atactic 1,2-polybutadiene can also be synthesized in good purity with suitable catalysts. For anionic polymerization with butyllithium or the coordinative process with Ziegler catalysts, 1,3-butadiene must be carefully purified from reactive contaminants such as acetylene, aldehydes, or hydrogen sulfide. A. Anionic Polymerization Metal alkyls, preferably of alkali metals, are used as initiators. The polarization of the catalyst exerts a strong influence on the stereospecifit y (Table 1) [15,16]. Lithium alkyls give a polymer with the great est trans-1,4-portion. The stereospecifity is also influenced by catalyst concentrations, temperatures, and associative behavior [17–34]. In more concentrated solutions, alkyllithium, especially butyllithium, which is the preferred initiator, forms hexameric associates that are dissociated in several steps to finally give monomers [35–53]. Only mon omeric butyllithium is suited for the insertion. Isobutyl- lithium shows an association grade of 4 in cyclohexane [36]. Branched alkyl groups gave higher activities than those with n-alkyl groups. As postulated by the kinetic model for very weak initiator concentration, the reaction order is 1 and less than 1 for higher concentrations [54–62]. This results in a series of reactions: Dissociation: ðCH 3 ÀðCH 2 Þ 3 ÀLiÞ 6 ! 6CH 3 ÀðCH 2 Þ 3 À Li ð4Þ Start: CH 3 ÀðCH 2 Þ 3 ÀLi þ CH 2 ¼CHÀCH¼CH 2 ! CH 3 ÀðCH 2 Þ 3 ÀCH 2 ÀCH¼CHÀCH 2 ÀLi ð5Þ Propagation: CH 3 ÀðCH 2 Þ 4 ÀCH¼CHÀCH 2 ÀLi þ CH 2 ¼CHÀCH¼CH 2 ! CH 3 ÀðCH 2 Þ 3 ÀðCH 2 ÀCH¼CHÀCH 2 Þ 2 ÀLi ð6Þ Table 1 Microstructure of poly(1,3-butadiene) in relation to the initiator. Microstructure (%) Initiator Solvent cis trans 1,2 C 2 H 5 Li Hexane 43 50 7 C 2 H 5 Li THF 0 6 91 C 4 H 9 Li Hexane 35 55 10 C 10 H 8 Li THF 0 3.6 96.4 C 10 H 8 Na THF 0 9.2 90.8 C 10 H 8 K THF 0 17.5 82.5 C 10 H 8 Rb THF 0 24.7 75.3 C 10 H 8 Cs THF 0 25.5 74.5 Source: Refs. [15] and [17]. Copyright 2005 by Marcel Dekker. All Rights Reserved. With hydrocarbons as solvents, the rate of the starting reaction is up to a factor of 100 smaller than that of the propagation step. This difference is caused by the absence of a double bond in conjugation to lithium in butyllithium. In contrast to this, the use of ether accelerates the starting reaction such that propagation becomes the rate-determining step [63–67]. In the absence of chain transfer reagents, the molecular weight increases steadily with increasing conversion of monomer. In this way one gets living polymers with very narrow molecular weight distribution when the starting reaction is fast or lithium octenyl is used as a starter (Poisson distribution). The average degree of polymerization is equal to the ratio of converted moles of monomer (st arting concentration [M ] 0 ) over the number of moles of initiator [I ] reacted: P n ¼ ½M  0 ½I  0 À½I  > ½M  0 ½I  0 ð7Þ At the end of the polymerizat ion when no more unreacted initiat or is present ([I ] ¼ 0), the number average of the molecular weight can be calculated as follows: M n ¼ ½M  0 ½I  0  54 ð8Þ Equation (9) is valid as long as there is still some monomer in the reaction mixture: ½M À½M  0 ¼ð½I  0 Þ 1 À kw kg  þ kw kg ½I  0 ln ½I  ½I  0 ð9Þ To improve the processibility of linear polybutadiene with its narrow molecular weight distribution, one can continuously add initiator in the course of the polymerization, vary the reaction temperature, or force long-chain branching by addition of divinyl compounds [68–74]. Addition of small amounts of ethers or tertiary amines alters the vinyl content from some 12% to more than 70% (Table 2). Bis(2-methoxy) ethyl ether and 1,2-bis(dimethylamino)ethane as well as crow n ethers [75,76] are particularly effective. The microstructures of the products are determinated by IR [77–87], NMR [88–99], x-ray diffraction, and other methods [100,101]. The anionic poymerization of 1,3-butadiene is normally carried out in solvents [102–109]. Aliphatic, cycloaliphatic, aromat ic hydrocarbons, or ethers as solvents could be used. Working in ethers requires low temperatures because of the high reactivity and low stability of the lithium alkyl in this solvent. Using n-hexane as solvent, a butadiene concentration of 25 wt% and a polymerization temperature of 100 to 200  C is preferred. Low-molecular-weight polybutadiene oils result when the polymerization is catalyzed by a mixed system of butyllithium, 1,2-bis(dimethylamino)ethane, and potas- sium t-butanolate [110–112]. With 1,4-dilithium-1,1-4,4-tetraphenylbutane it is possible to get bifunctional living polymers (seeding technique) [113–118]. B. Coordination Catalysts A large number of complex metal catalysts have been employed in the polymerization of conjugated dienes [119–139]. Table 3 shows a selection of catalyst systems that have Copyright 2005 by Marcel Dekker. All Rights Reserved. been used for the polymerization of butadiene. Some systems yield polymers with a high percentage of cis-1,4 linkage, while others favor the formulation of trans-1,4 or trans-1,2 linkages. As in the case of Ziegler–Natta catalysis of propene, the active centers are transition metal-carbon bonds. They normally form a  3 -alloyl bond [140]: ð10Þ Table 2 Influence of polar compounds on the microstructure (1,2 content) a . 1,2 Structure (wt%) for polymerization temperature Polar compound Molar ratio 30  C50  C70  C (H 3 C–O–CH 2 –CH 2 ) 2 O 0.10:1 51 24 14 0.45:1 77 56 28 0.80:1 77 64 40 (H 3 C) 2 N–(CH 2 ) 2 –N(CH 3 ) 2 0.06:1 26 14 13 0.60:1 57 47 31 1.14:1 76 61 46 Source: Ref. [73]. a Catalyst: C 4 H 9 Li. Table 3 Catalysts for the polymerization of 1,3-butadiene. Microstructure (%) Catalyst cis trans 1,2 Refs. TiCl 4 /R 3 Al 65 35 [123] TiJ 4 (R 3 Al 95 2 3 [124] Co(O-CO-R) 2 /(H 5 C 2 ) 2 Al-Cl/H 2 O 96 [125] Ni(O-CO-R) 2 /F 3 B-O(C 2 H 5 ) 2 /R 3 Al 97 [126] Ce(O-CO-R) 3 /(H 5 C 2 ) 3 Al 2 CL 3 /R 3 AL 97 [127] U(OCH 3 ) 4 /AlBr 3 /R 3 AL 98.5 1 0.5 [128] U(O-CO-C 7 H 15 ) 4 /AlBr 3 /R 3 Al 98.2 1.1 0.7 [129] Nd(O-CO-R)/R n AlCl 3-n /R 3 Al 98 1.5 0.5 [130,132] VCl 3 (VOCl 3 )/R 3 Al 99 1 [133,134] Cr(C 5 H 7 O 2 ) 3 /R 3 Al 8 2 90 [135] Rh(C 5 H 7 O 2 ) 3 a /R 3 Al 98 [136] Cr(allyl) 3 10 90 [120] Nb(allyl) 3 1 2 97 [121] Cr(allyl) 2 Cl 90 5 5 [144] a 2,4-Pentandionato. Copyright 2005 by Marcel Dekker. All Rights Reserved. The propagation reaction proceeds via insertion into these carbon–transition metal bonds after the diene has been coordinated as a p-complex: ð11; 12Þ In the transition state a short-lived s-allyl bond is formed, which in the case of cis migration, restores an alkyl-transition metal bond [141–143]. Various mechanisms for the control of the cis linkage in the propagation step are discussed [144,145]. Allyl compounds can occur in syn or anti form [Structures (13–16)], from which double bonds with trans or cis configuration are formed [146,147], respec- tively. Solvents or cocatalysts as ligands are of great importance for the equilibration. ð13À16Þ C. cis-1,4-Polybutadi ene cis-1,4-Polybutadiene is preferrentially produced with mixed catalysts. Systems on the basis of titanium (IV) iodine/trialkylaluminum are employed [148–150]. For better dosing a mixture of TiCl 4 /I 2 /R 3 Al, TiCl 4 /R 2 All, or Ti(OR)I 3 /TiCl 4 /(C 2 H 5 ) 3 Al in which all Copyright 2005 by Marcel Dekker. All Rights Reserved. compounds are soluble in hy drocarbons, is used. It is essential for a high cis content of the products that the catalyst contains iodine. Those of TiCl 4 and R 3 Al only lead predominantly to the formation of trans-1,4-polybutadiene. Aromatic hydrocarbons (benzene, toluene) are used as solvents. The polymerization is a first-order reaction with respect to the 1,3-butadiene concentration [150,151]. As TiCl 4 gives living polymers, the molecular weight increases almost linearly with the conversion of monomer [152]. At higher degrees of conversion, the molecular weight can be controlled by varying the catalyst concentration or composition. The molecular weight distribution M w /M n ranges from 2 to 4 with a cis content between 90 and 94%. Regulation of molecular weights can be achieved by the addition of 1,5-cyclo-octadiene [153]. Supported Ziegler catalysts are also used [154–156]. High cis contents up to 98% can be obtained with cobalt salts [cobalt octanoate, cobalt naphthenate, tris(2,4-penta- dionato) cobalt] in combination with alumoxanes which are synthesized in situ by hydro- lysis of chlorodiethylaluminum or ethylaluminum sesquichloride. Only 0.005 to 0.02 mmol of cobalt salt is needed for the polymerization of 1 mol of 1,3-butadiene [157–159]. At 5  C the molecular weight varies from 350 000 to 750 000 depending on the alkylaluminum chloride, while at 75  C the variation is between 20 000 and 200,000. The polymerization rates are fast over a considerable range of chloride content. The cis-1,4-structure increases with chlorid e content. The molecular weight increases with the chloride level [160]. Nickel compounds can also be employed as catalysts [161–170]. A three-component system consisting of nickel naphthenate, triethyl-aluminum, and boron trifluoride diethyletherate is used technically. The activities are similar to those of cobalt systems. The molar Al/B ratio is on the order of 0.7 to 1.4. Polymerization temperatures range from À5to40  C. On a laboratory scale the synthesis of cis-1,4-polybutadiene with allylchloronickel giving 89% cis, 7.7% trans, and 3.4% 1,2-structures is particularly simple [8]. In nickel compounds with Lewis acids as cocatalysts, complexes with 2,6,10- dodecatriene ligands are more active than those with 1,5-cyclooctadiene (Table 4) [171]. The influence of the ligand on cis or trans insertion is particularly obvious for  3 -allyl nickel systems. ð17À20Þ Copyright 2005 by Marcel Dekker. All Rights Reserved. Alkanolates or carboxylates of lanthanides and actinides, especially uranium, are particularly well suited for the production of cis-1,4-polybutadiene [172–187]. Of the lanthanides, compounds of cerium, praseodymium, and neodymium are combined with trialkylaluminum and a halogen containing Lewis acid [188,189]. The polymerization can also be carried out in aliphatic solvents at 20–90  C [190]. The microstructures are influenced primarily by the nature of the alkylaluminum compound. With triethylaluminum the portion of trans-1,4 double bonds reaches a relatively high level of 10%, while tris(2-methylpropyl)aluminum and bis(2-methylpropyl) aluminum hydride yield cis-1,4 contents as high as 99% [190]. Similarly, high cis-1,4 portions are obtained in the polymerization of 1,3-butadiene with  3 -allyluranium complexes. The osmometric measured mole mass ranges from 50 to 150 000, the molecular mass distribution between 3 and 7. The extremely high temperature-induced crystallization rate of uranium polybutadiene in comparison with titanium or cobalt polybutadiene corresponds to a greater tendency tow ard expansion-induced crystallization. A technical application, however, is in conflict with the costly removal of weakly radioactive catalyst residues from the products [132]. 1. Metallocene-catalysts Different methyl substituted cyclopentadienyl titanium compounds can be employed as catalysts (Table 5) [191]. At a polymerization temperature of 30  C the chlorinated and the fluorinated complexes show nearly the same activity. Only the highly substituted fluorinated compounds (tetra- and pentamethylcyclopentadienyl titanium trichloride Me 4 CpTiF 3 , Me 5 CpTiF 3 ) are significantly more active than the corresponding chlorinated ones. At higher polymerization temperatures a corresponding behavior can be observed, however with increasing polymerization temperature also the activity of the complexes increase. The activities of the 1,3-dimethylcyclopentadienyl titanium trihalides are the highest and reach about 700 kg Br/mol Ti * h. It makes no difference if one of the fluorides is substituted by another ligand like perfluoroacetic or perfluorobenzoic acid (Me 5 CpTi- F 2 (OCOCF 3 ), Me 5 CpTiF 2 (OCOC 6 F 5 )). The activity reaches a maximu m value for all catalysts after a short induction period of 5 to 10 min. After this, the activity decreases to a value being constant for a longer period of time of up to about 1 h. The substitution pattern influences the induction period. The most active com- pounds show the shortest induction period, whereas the less active ones need a clearly longer period. Table 4 Polymerization of 1,3-butadiene. a Cocatalyst Molar ratio, HX/Ni Reaction time (h) Yield (%) cis-1,4 (%) trans-1,4 (%) 1,2 (%) HCl 1 3 13 84 13 3 HBr 1 3 4 72 25 3 HJ 1 6 30 0 100 0 Source: Ref. [161]. a 3,4 mol butadiene, 0.014 mol of 2,6,10-dodecatrienylchloronickel at 55  C in heptane. Copyright 2005 by Marcel Dekker. All Rights Reserved. The activity increases linear with increasing butadiene concentrations in the starting phase of the polymerization. The kinetic order of the butadiene concentration is 1. At constant Al:Ti ratio the polymerization rate is given by r p ¼ k p Á c cat Á c b ð21Þ where c b is the concentration of butadiene. The activity increases with an increasing Al:Ti ratio, reaches a maximum at an Al:Ti ratio of about 700 and decreases slowly with increasing Al:Ti ratios. High molecular weights are obtained for the polybutadienes produced with these catalysts. The di- and trimethylcyclopentadienyl titanium trichlorides give the highest molecu- lar weights while the fluorinated compounds have significantly lower molecular wei ghts, even if their activity is higher, as shown for the Me 4 CpTiF 3 and Me 5 CpTiF 3 complexes (Table 6). The glass transition temperatures range of À90.1 and À96.9  C. The polybutadienes produced with the most active catalysts have the highest content of cis-1,4 units and the lowest glass transition temperature. For all catalysts, the cis-1,4 structure units of the polybutadiene range between a content of 74 and 85.8%, the trans -1,4 between 0.5 and 4.2%, and the 1,2-units between 13.7 and 22.6% (Table 7). The most active systems generate the polymer with the highest content of cis-1,4 and the lowest content of trans-1,4 and 1,2-units. The fluorinated compounds show a similar behavior. A mechanism for the formation of these micro- structures is published by Porri [192]. There is no dependence of the microstructure on the polymerization time (between 10 and 120 min the cis content is 81.8 Æ 0.3% for MeCpCl 3 ) and on the Al:Ti ratio (between Al:Ti ¼ 500 and Al:Ti ¼ 10 000 the cis content is about 80.7 Æ 1.2 for MeCpTiF 3 ). D. trans-1,4-Polybu tadiene Butadiene can be polymerized with Ti/Al catalyst systems. A sharp change in structure of polybutadiene can be seen by varying the mole ratio of TiCl 4 to R 3 Al. At Ti/Al ratios of Table 5 Activities of titanium complexes for the polymerization of 1,3-butadiene in 100 ml toluene, 10 g 1,3-butadiene, 0.29 g MAO, [Ti] ¼ 5  10 À5 mol/l, Al/Ti ¼ 1000, T ¼ 30  C, poly- merization time ¼ 20 min. Catalyst Activity a Catalyst Activity a CpTiCl 3 260 CpTiF 3 260 MeCpTiCl 3 300 MeCpTiF 3 310 Me 2 CpTiCl 3 750 Me 2 CpTiF 3 605 Me 3 CpTiCl 3 340 Me 3 CpTiF 3 350 Me 4 CpTiCl 3 165 Me 4 CpTiF 3 350 Me 5 CpTiCl 3 60 Me 5 CpTiF 3 350 IndTiCl 3 310 Cp*TiF 2 (OCOCF 3 ) 330 PhCpTiCl 3 325 Cp*TiF 2 (OCOC 6 F 5 ) 340 a Activity: kg BR/ mol Ti*h. Copyright 2005 by Marcel Dekker. All Rights Reserved. 0.5 to 1–5, the cis content of the 1,4-polybutadiene increases to about 70% at a ratio of 1, and then falls off so that trans-1,4-polybutadiene is obtained at Ti/Al ratios of 1.5 to 3. Under these conditions it is a good catalyst for preparing trans-1,4-polybutadiene. Also heterogeneous catalysts consisting of TiCl 4 immobilized on MgCl 2 have been reported [193]. Other catalysts contain the transition metals vanadium, chromium, cobalt, and nickel as their main components [194–202]. The polymerization activity is usually far lower than in the synthesis of cis polymers (see Table 2). Addition of a donor such as tetrahydrofuran, which directs the bonds into a trans-position to the catalyst of titanium tetraiodide and triethylaluminum, results in the formation of a polybutadiene with 80% trans-1,4-double bonds [197]. Table 6 Molecular weights of the polybutadienes produced with fluorinated and chlorinated catalysts. Catalyst X ¼ Cl Molar mass M  [g/mol  10 6 ] X ¼ F Molar mass M  [g/mol  10 6 ] CpTiX 3 1.2 0.97 MeCpTiX 3 1.6 1.22 Me 2 CpTiX 3 3.1 1.28 Me 3 CpTiX 3 3.6 1.25 Me 4 CpTiX 3 3.3 1.5 Me 5 CpTiX 3 2.6 1.4 IndTiCl 3 1.25 – PhCpTiCl 3 0.86 – CyCpTiCl 3 1– (Me 3 Si,MeCp)TiCl 3 1.5 – Table 7 Microstructure and glass transition temperatures of polybutadienes produced with chlorinated and fluorinated catalyst precursors. Catalyst cis-1,4 [%] trans-1,4 [%] 1,2 [%] T g [  C] CpTiCl 3 81.7 1.1 17.2 À 95.1 MeCpTiCl 3 81.9 1.1 17 À 95.3 Me 2 CpTiCl 3 85.8 0.5 13.7 À 96.9 Me 3 CpTiCl 3 83.8 1.1 15.2 À 95.6 Me 4 CpTiCl 3 80 1.7 18.3 À 91.5 Me 5 CpTiCl 3 74.8 2.6 22.6 À 91 IndTiCl 3 74.3 4.2 21.5 À 90.1 PhCpTiCl 3 80.9 2.1 16.9 À 95.8 CyCpTiCl 3 82.6 0.8 16.7 À 95 CpTiF 3 81.8 1.4 16.8 À 95 MeCpTiF 3 81.9 1.2 16.9 À 92.7 Me 2 CpTiF 3 82 2 16 À 95 Me 3 CpTiF 3 84 1.1 14.9 À 94.1 Me 4 CpTiF 3 80.4 1.9 17.7 À 89.9 Me 5 CpTiF 3 74.6 2.8 22.5 À 87.9 Copyright 2005 by Marcel Dekker. All Rights Reserved. Another possibility is anionic polymerization with alkyllithium in combination with barium compounds such as barium 2,4-pentanedionate [192–194, 203–205]. Also, cobalt(II) chloride in combination with diethylaluminum chloride and triethylamine is used, yielding a polymer with 91% trans-1,4 and 9% 1,2 structures. E. 1,2-Polybutadiene The synthesis of crystalline, syndiotactic 1,2-polybutadiene is also successful with compounds of titanium, cobalt, vanadium, and chromium [194,206–210]. Alcoholates [e.g., cobalt(II) 2-ethylhexanoate or titanium(III) butanolate] with triethylamine as cocatalyst, are especially well suited for this purpose. They are capable of producing polymers with up to 98% 1,2 structure. Amorphous 1,2-polybutadiene is produced with molybdenum(V) chloride and diethylmethoxyaluminum [211]. Addition of esters of carboxylic acids raises the vinyl content of the products [212]. The influence of the coordination at the center atom is remarkable. Trisallylchromium polymerizes 1,3- butadiene to 1,2-polybutadiene, while bisallylchro mchloride gives 1,4-polybutadiene. ð22À23Þ 1. Polymerization Processes Polybutadiene can be produced in nonaqueous media or by a radical mechanism in an aqueous emulsion. The field of homopolymerizations is dominated by the processes in nonaqueous media, as described. Emulsion polymerization is characterized by good dissipation of the reaction heat. The monomer concentration is on the order of 50 wt %. The reaction is initiated by free radicals, which are preferably formed from organic hydroperoxides such as p-menthane hydroperoxide [213,214]. Sodium formaldehyde sulfoxylate and iron(II) complexes are employed as reducing agents. At reaction temperatures below 5  C the polymerization is discontinued at a degree of conversion between 50 and 60%, to avoid cross-linking. The product features low stereospecifity (14% cis-1,4, 69% trans-1,4, and 17% 1,2 struc tures). At higher temperatures degradation of the polybutadiene lowers the molecular weight [215,216]. III. POLYISOPRENE The homopolymerization of isoprene ð24Þ Copyright 2005 by Marcel Dekker. All Rights Reserved. [...]... 1,3-butadiene [54 8 ,54 9], acrylonitrile [55 0 ,55 1], SCl2 [55 2], SO2 [55 3], and compounds of maleic acid [55 4 55 7] Nonconjugated dienes as ethylidene norbornene, dicyclopentadiene, and 1,4hexadienes are used as diene components in ethene-propene-diene-monomer (EPDM) elastomers [55 8 56 4] The copolymers are synthesized with Ziegler–Natta catalysts Vanadium compounds also give living copolymers of propene and 1 ,5- hexadiene... AlEtCl2 0.38 0.38 0 .53 0 .53 16 0.79 0.79 trans cis trans cis trans trans trans Source: Ref [3 75] Copyright 20 05 by Marcel Dekker All Rights Reserved H2O/catalyst (mol/mol) Gel (%) Double bond (%) 1,4 1,2 3,4 1.00 1.00 0. 65 0.70 0.02 0.01 0.10 12 15 0 16 0 0 15 79 85 89 78 .5 76 91.6 60 .5 47.1 52 .5 46 .5 23.8 40 60.4 41 .5 18.6 19 .5 21.0 21.2 16 25. 6 12 .5 0 0 0 0 0 0 3 Table 18 Polymerization of methyl-1,3-pentadiene... the cis polymer is À 20  C at a degree of crystallinity of about 12% Copyright 20 05 by Marcel Dekker All Rights Reserved Table 12 Microstructure of polychloroprene as related to polymerization temperature trans-1,4 12 30 42 57 70 Head/tail (%) Head/head, tail/tail (%) cis-1,4 (%) 1,2 (%) 3,4 (%) 83.0 81 .5 80 .5 80 .5 75. 0 Temp.( C) 11 .5 12.0 12.0 11.0 13 .5 3.8 4 .5 5.2 5. 8 8.4 1.0 1.2 1.2 1.4 1 .5 0.8... styrene [53 0] Quirk [53 1] reports on the copolymerization of myrcene and styrene Block copolymers with molecular weight of more than 100 000 are obtained Many combinations of substituted 1,3-butadienes and cyclodienes with other dienes, olefins, and styrene have been described [53 2 54 2] Cyclopentadiene or 1,3-cyclohexadiene can be copolymerized with a-methylstyrene [54 3 54 5], isobutene [54 6 ,54 7], 1,3-butadiene... 20 15 20 20 20 26 26 78 50 57 85 82 2 31 45 65 (5) 82 93 61 68 55 35 95 18 7 29 20 0 0 0 0 0 10 Cationic polymerization provides, independent of the isomer of the 1,3-pentadiene, high trans-1,4 and trans-1,2 microstructures (Table 17) Studies on the insertion mechanism and the various side reactions have been carried out [373,374] In principle, 1,4-disubstituted butadienes can give different types of. .. hydrogenation of the double bond yields nitrile rubbers with a low swelling capacity D Isoprene Copolymers With the aid of Ziegler catalysts it is possible to copolymerize isoprene with ethene and other a-olefins Just like the analogous butadiene copolymers, the products are of alternating structure [51 8 52 1] Copolymerization of isoprene with acrylic monomers is also possible [51 6 ,52 2 ,52 3] The copolymers... catalyst The copolymer has a glass transition temperature of À60  C E Copolymers of Other Dienes 1-Chloro-1,3-butadiene can be polymerized with styrene [52 8] The anionic block copolymerization of 1- or 2-phenyl-1,3-butadiene with styrene leads to block polymers of low molecular weight [52 9] Similar copolymers are described of 1,3-pentadiene with styrene With alkyllithium there is no reaction of 1,4-diphenyl-1,3-butadiene... Reserved Table 21 Polymerization of 1,3-cyclohexadiene with napthalene alkali metals Catalyst metal Catalyst (mol/l) Li Li Na K Li Na Na 4.0 4.3 7. 95 7 .52 1.7 2.34 3.28 Solvent THF THF THF THF DME DME DME Temp ( C) Time (h) Yield (%) Mn Mw/Mn 25 À20 25 25 À20 29 À73 2 1.2 1.6 0.2 13 .5 19 2 .5 48 96 62 61 95 48 81 13 000 12 600 4 300 2 400 19 000 57 0 38 700 1.48 1.19 1 .57 1.48 1.44 1. 45 Source: Ref [421]... 20 05 by Marcel Dekker All Rights Reserved [4 35] there is a 1:1 ratio between trans and cis five-membered rings: ð64Þ At a polymerization temperature of 22  C, approximately 80% of the cyclopentane rings in the polymer are trans Table 23 shows some other examples of the polymerization of nonconjugated dienes to cyclic units [320] VIII A COPOLYMERIZATION OF DIENES 1,3-Butadiene-Styrene-Copolymers Copolymers... 20 05 by Marcel Dekker All Rights Reserved Table 11 Homopolymerization of isoprene Polymerization conditions: 50 ml toluene, 50 ml isoprene [Ti] ¼ 5  10 5 mol/l, Al/Ti ¼ 200, Tp ¼ 30  C, tp¼ 5 24 h Catalyst CpTiCl3 Me5CpTiCl3 CpTiF3 MeCpTiF3 Me5CpTiF3 Activity [g IR/mol Ti-h] Tg [ C] ‘28 8 840 250 29 52 n.b 50 .3 n.b n.b As of steric effects the unsubstituted cyclopentadienyl compound is more active . 3,4 (%) 12 83.0 11 .5 3.8 1.0 0.8 30 81 .5 12.0 4 .5 1.2 1.0 42 80 .5 12.0 5. 2 1.2 1.1 57 80 .5 11.0 5. 8 1.4 1.3 70 75. 0 13 .5 8.4 1 .5 1.4 Source: Refs. [297] and [299]. Copyright 20 05 by Marcel Dekker hydro- lysis of chlorodiethylaluminum or ethylaluminum sesquichloride. Only 0.0 05 to 0.02 mmol of cobalt salt is needed for the polymerization of 1 mol of 1,3-butadiene [ 157 – 159 ]. At 5  C the molecular. MeCpTiF 3 310 Me 2 CpTiCl 3 750 Me 2 CpTiF 3 6 05 Me 3 CpTiCl 3 340 Me 3 CpTiF 3 350 Me 4 CpTiCl 3 1 65 Me 4 CpTiF 3 350 Me 5 CpTiCl 3 60 Me 5 CpTiF 3 350 IndTiCl 3 310 Cp*TiF 2 (OCOCF 3 ) 330 PhCpTiCl 3 3 25 Cp*TiF 2 (OCOC 6 F 5 )