rac-[CH2(3-tert-butyl-1-indenyl)2]ZrCl2/MAO in the Copolymerization of Olefins and Dienes

Olefin-diene copolymerizations in the presence of C₂ symmetric zirconocene rac-[CH₂(3-tert-butyl-1-indenyl)₂]ZrCl₂/MAO catalytic system have been reported and rationalized by experimental and molecular modeling studies. Ethene gives 1,2-cyclopropane and 1,2-cyclopentane, 1,3-cyclobutane, and 1,3-cyclopentane units in copolymerization with 1,3-butadiene, 1,4-pentadiene, and 1,5-hexadiene, respectively. Propene-1,3-butadiene copolymerizations lead to 1,2 and 1,4 butadiene units and to a low amount of 1,2-cyclopropane units.     

Prins-Reaktionen mit Arylaldehyden, 2. Mitt. Diene

By 1,4-addition of arylaldehydes to 2,3-dimethyl-1,3-butadiene in the presence of sulfuric acid 2-aryl-4,5-dimethyl-3,6-dihydro-2H-pyrans are obtained. From 1,3-butadiene and isoprene beside the corresponding 3,6-dihydro-2H-pyrans by reaction with two more molecules aldehydetrans-2,4,7-triphenyl-4a,7,8,8a-tetrahydro-4H,5H-pyrano[4,3-d-1,3-dioxines are formed. With 1,3-cyclohexadiene, however, 1,2-addition of benzaldehyde is observed to givecis-r-2,c-4-diphenyl-4a,5,6,8a-tetrahydro-1,3-benzodioxane.     

Monomer distributions and number-average sequence lengths in hydrogenated butadiene–styrene copolymers from carbon-13 nuclear magnetic resonance

Monomer distributions and number-average sequence lengths are determined from ¹³C nuclear magnetic resonance (NMR) data for 1,4- and 1,2-butadiene additions and styrene additions in a series of four hydrogenated butadiene–styrene copolymers. The monomer distribution is expressed in terms of the six unique days from which it is possible to calculate the number-average sequence length of each monomer type. Carbon-13 NMR spectral assignments are given and the techniques for making the assignments are discussed. The method presented could, in principle, be applied to any copolymer or terpolymer. Limitations that are encountered in the analysis of hydrogenated butadiene–styrene copolymers high in 1,2 additions are discussed.     

N,N-dihalophosphoramides-XV: The addition of diethyl N,N-dichlorophosphoroamidate (DCPA) to conjugated 1,3-dienes

The addition of DCPA to several conjugated 1,3-dienes has been studied. The reaction was found to proceed in dichloromethane and was spontaneously or photolytically initiated depending on the structure of the dienes. N-chloro adducts, formed upon addition, could be reduced “in situ” with sodium sulphite solution to give the corresponding diethyl N-(chloroalkenyl)posphoroamidates. Addition of DCPA to terminal double bond 1,3-dienes (butadiene, isoprene and 2,3-dimethyl-1,3-butadiene) leads regiospecifically to (E)-1,4-adducts. Similarly, 1,4-addition is also observed for 1,3-cyclohexadiene. Reaction of DCPA with nonterminal double bond 1,3-dienes (trans-piperylene, 4-methyl-1,3-pentadiene, 2,5-dimethyl-2,4-hexadiene and 1,4-diphenyl-1,3-butadiene) usually affords a mixture of adducts. Spectral data and chemical transformations pertinent to the proof of structure of DCPA addition products are presented. A possible mechanism for the addition is discussed.     

Bis-Pyrazolones as azodienophiles

Lead tetraacetate oxidations of 2,3,3a,4,6,7,7a,8-octahydrobenzo[1,2-c:4,5-c']dipyrazolo-3,7-dione and 2,3,3a,4,5,5a,6,7-octahydrobenzo[2,1-c:3,4-c']dipyrazolo-3,6-dione in the presence of 1,3-cyclopentadiene, 1,3-cyclohexadiene, 2,3-dimethyl-1,3-butadiene or 1,4-diphenyl-1,3-butadiene have yielded octahydrodipyridazino[1,2-a:1,2-a']benzo[1,2-c:4,5-c']dipyrazolo-6,14-diones and octahydrodipyridazino[1,2-a:1,2-a']benzo[2,1-c:3,4-c']dipyrazolo-6,9-diones. In one of the eight Diels-Alder reactions two isomeric products were isolated.     

Polyaromatic ether-ketone-sulfones containing 1,3-butadiene units

The acid chloride of 1,4-bis-p-carboxyphenyl-1,3-butadiene (XI) and isophthaloyl chloride (XIV) were polymerized with 4,4′-diphenoxy-diphenyl sulfone (XII) and diphenyl ether (XIII) in a Friedel-Crafts type of polymerization. The polymers obtained, which contained 5–20 mole % of butadiene units, were insoluble in all solvents. The polyamides prepared from the acid chloride of 1,4-bis-p-carboxyphenyl-1,3-butadiene (XI) and aromatic diamines were also insoluble in all solvents.     

Prins-Reaktionen mit Arylaldehyden, 2. Mitt. Diene

By 1,4-addition of arylaldehydes to 2,3-dimethyl-1,3-butadiene in the presence of sulfuric acid 2-aryl-4,5-dimethyl-3,6-dihydro-2H-pyrans are obtained. From 1,3-butadiene and isoprene beside the corresponding 3,6-dihydro-2H-pyrans by reaction with two more molecules aldehydetrans-2,4,7-triphenyl-4a,7,8,8a-tetrahydro-4H,5H-pyrano[4,3-d-1,3-dioxines are formed. With 1,3-cyclohexadiene, however, 1,2-addition of benzaldehyde is observed to givecis-r-2,c-4-diphenyl-4a,5,6,8a-tetrahydro-1,3-benzodioxane.

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Herrn Prof. Dr.Anton v. Wacek, emerit. Vorstand des Instituts für Organische Chemie und Organisch-chemische Technologie der Technischen Universität Graz, in Verbundenheit zum 80. Geburtstag gewidmet.

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1. Mitt.:H. Griengl undK. P. Geppert, Mh. Chem.107, 421 (1976).     

Hydrocarbon polymers containing six-membered rings in the main chain. Microstructure and properties of poly(1,3-cyclohexadiene)

The relationship between the microstructure and the properties of poly(1,3-cyclohexadiene)s, obtained by living anionic polymerization with an alkyllithium/amine system, and their hydrogenated derivatives are reported. The 1,2-bond/1,4-bond molar ratio of poly(1,3-cyclohexadiene) was determined by measuring 2D-NMR with the H H COSY method. The glass transition temperature of poly(1,3-cyclohexadiene) was found to rise with an increase in the ratio of 1,2-bonds to 1,4-bonds or with an increase of the number average molecular weight. The 1,2-bond of the polymer chain gives a high flexural strength and heat distortion temperature. Hydrogenated poly(1,3-cyclohexadiene) has the highest T_g (231°C) among all hydrocarbon polymers ever reported. 1,3-Cyclohexadiene–butadiene–1,3-cyclohexadiene triblock copolymer and 1,3-cyclohexadiene–styrene–1,3-cyclohexadiene triblock copolymer have high heat resistance and high mechanical strength. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1657–1668, 1998     

Copolymerization of propylene with 1,3‐butadiene using isospecific zirconocene catalysts

Poly(propylene‐ran‐1,3‐butadiene) was synthesized using isospecific zirconocene catalysts and converted to telechelic isotactic polypropylene by metathesis degradation with ethylene. The copolymers obtained with isospecific C₂‐symmetric zirconocene catalysts activated with modified methylaluminoxane (MMAO) had 1,4‐inserted butadiene units ( 1,4‐BD ) and 1,2‐inserted units ( 1,2‐BD ) in the isotactic polypropylene chain. The selectivity of butadiene towards 1,4‐BD incorporation was high up to 95% using rac‐dimethylsilylbis(1‐indenyl)zirconium dichloride (Cat‐A)/MMAO. The molar ratio of propylene to butadiene in the feed regulated the number‐average molecular weight (M_n) and the butadiene contents of the polymer produced. Metathesis degradations of the copolymer with ethylene were conducted with a WCI₆/SnMe₄/propyl acetate catalyst system. The ¹H NMR spectra before and after the degradation indicated that the polymers degraded by ethylene had vinyl groups at both chain ends in high selectivity. The analysis of the chain scission products clarified the chain end structures of the poly(propylene‐ran‐1,3‐butadiene). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5731–5740, 2007     

New processable polyaromatic ether–keto-sulfones curable by Diels-Alder cycloaddition

New Processable polyaromatic ether-keto-sulfones were prepared from the acid chloride of bis-m-carboxyphenyl acetylene (XII), isophthaloyl chloride (XX), diphenyl ether (XVIII), and 4,4′-diphenoxydiphenyl sulfone (XIX) in a Friedel-Crafts-type polymerization. These polymers were cured by Diels-Alder cycloaddition with 1,4-diphenyl-1,3-butadiene. The cured polymers showed an increase in T_g and in thermal and heat stabilities. The polymers form colorless, transparent, brittle films and can be cast into a glass fiber laminate. Both meta-and para-substituted acid chlorides of biscarboxyphenyl-1,3-butadiene yielded insoluble polymers under the same conditions but form processable polymers where combined with acetylene units in the polymer chain. Polymers that contained both acetylene and butadiene units were prepared but could not be cured by an intramolecular Diels-Alder cycloaddition reaction.     

Anionic synthesis of polystyrene and polybutadiene heteroarm star polymers

The use of living linking reactions of poly(styryl)lithium with 1,3-bis(1-phenylvinyl)benzene followed by crossover reactions with styrene or butadiene monomers has been used to prepare four-armed heteroarm, star-branched polymers. Bimodal molecular weight distributions have been observed for crossover reactions with both styrene and butadiene. Addition of THF ([THF]/[Li]=14–32) for crossover to styrene and lithium sec-butoxide for crossover to butadiene produces monomodal molecular weight distributions. Symmetrical, four-armed star polystyrenes have been synthesized; properties have been compared with a corresponding polymer prepared via a silicon tetrachloride linking reaction. Heteroarm, star-branched polymers with two polystyrene arms and two polybutadiene arms with high 1,4-microstructure have been prepared.     

Synthesis and polymerization of 1- and 2-cyano-1,3-butadienes

1-Cyano-1,3-butadiene and 2-cyano-1,3-butadiene were prepared and designated 1-cyanoprene and 2-cyanoprene, respectively. These compounds, and their intermediates, were characterized by their infrared and proton magnetic resonance spectra. Their polymerizations with lithium or aluminum alkyl catalysts are described. The synthesis of these monomers involves a thermal cracking process (400–500°C). The yield of monomer by this process depends on the positions of the cyano and acetoxy groups in the butene intermediate; if the cyano and the acetoxy groups are attached to the same allylic carbon, a low monomer yield is obtained. The polymers of 1-cyanoprene are the results of 1,4-enchainment (cis and trans) and are amorphous; the polymers of 2-cyanoprene may involve 1,4-enchainment but are partially crystalline. Both of these polymers are thermoplastic.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="Italic">N,N</Emphasis>-bis(silatranylmethyl)amine with trichlorosilane

N,N-Bis(silatranylmethyl)methylamine reacts with trichlorosilane to form the amine hydrochloride and perchloropolysilane, the product of polymerization of dichlorosilylene. In the presence of 1,3-butadiene the main products of the reaction are the amine hydrochloride and 1,1-dichlorosilacyclopentene-3, the product of 1,4-addition of dichlorosilylene to 1,3-butadiene.     

Preparation,copolymerization kinetics,and viscoelastic behavior of copolymers of 1,3-butadiene and 1,4-diphenyl-1,3-butadiene

1,4-Diphenyl-1,3-butadiene reacts readily with sec-butyllithium in toluene to form adducts. Although this 1,4-substituted conjugated diene did not homopolymerize or copolymerize with styrene, with butadiene it formed copolymers having compositions varying from one end of the chain to the other. The monomer reactivity ratios found were r₁ = 8.2, r₂ = 0 in toluene and r₁ = 2.1, r₂ = 0 in toluene–tetrahydrofuran (0.2%) solution. The intramolecular composition distribution of these polymers varied from an initial butadiene-rich composition, dependent on the ratio of monomers charged, to the equimolar composition of the alternating copolymer. In spite of this compositional heterogeneity, the crosslinked polymers exhibited a single glass transition characteristic of the mean composition. A secondary, high-temperature dispersion observed in the dynamic viscoelastic properties of some of the products is shown to be attributable to network topological effects.     

Filler‐polymer interactions of styrene and butadiene units in silica‐filled styrene–butadiene rubber compounds

Styrene–butadiene rubber (SBR) is a copolymer of styrene and butadiene, and the butadiene unit is composed of cis‐1,4‐, trans‐1,4‐, and 1,2‐components. Filler‐polymer interactions of each component of SBR in silica‐filled SBR compounds were examined by microstructure analysis of the bound and unbound rubbers. The composition ratio of butadiene and styrene units (butadiene/styrene) of the bound rubber was higher than that of the compounded rubber. Of the butadiene units, the 1,2‐component of the bound rubber was more abundant than the cis‐1,4‐ and trans‐1,4‐components. The filler‐polymer interaction of the butadiene unit with silica was stronger than that of the styrene unit, and the interaction of the 1,2‐component was stronger as compared with the others. The butadiene–styrene ratio of the bound rubber of the compounds containing the silane coupling agent was lower than for the compounds without the silane. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 577–584, 2004     

An Investigation of the Structure of Copolymers of lsobutylene and Diene Prepared by Initiation with VCI4 in the Dark and with Visible Light

¹H-NMR spectra of copolymers of isobutylene and 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene were investigated in connection with the elucidation of the formation of soluble and insoluble copolymers. For copolymers soluble in heptane, benzene, and CCI₄ it was found that the incorporation of diene into the polymer chain proceeds by 1,4-addition in the case of copolymerizations conducted both in the dark and with visible light using VC1₄ as initiator. The formation of a soluble and an insoluble copolymer is attributed to a different type of initiation, either with radical-cations of isobutylene, if soluble copolymers are formed, or with radical-cations of diene, if the arising copolymers are insoluble.     

Diacetoxylation of conjugated dienes with thallium(III) acetate in acetic acid

The reaction of conjugated dienes such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2,5-dimethyl-2,4-hexadiene, 1,3-cyclopentadiene, and 1,3-cyclohexadiene, with thallium(III)acetate in acetic acid at 10–65° for 0.5–15 hr affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products) in 10–92% yields. The 1,2-addition products are predominantly formed in all cases examined except the case of 1,3-cyclopentadiene. The reaction is assumed to proceed through acetoxythallation and dethallation steps, the latter step being accompanied and/or followed by an attack of acetoxyl group. An initial attack of thallium moiety is proposed to occur mainly at C-1 and C-2 carbons in the cases of linear terminal dienes and cyclic dienes, respectively.     

Diethylbis(2,2′‐bipyridine)iron/MAO. A Very Active and Stereospecific Catalyst for 1,3‐Diene Polymerization

Diethylbis(2,2′‐bipyridine)Fe/MAO is an extremely active catalyst for the polymerization of 1,3‐dienes. Polymers with a 1,2 or 3,4 structure are formed from butadiene, isoprene, (E)‐1,3‐pentadiene and 3‐methyl‐1,3‐pentadiene, while cis‐1,4 polymers are derived from 2,3‐dimethyl‐1,3‐butadiene. The 1,2 (3,4) polymers obtained at 25°C are amorphous, while those obtained below 0°C are crystalline, as was determined by means of X‐ray diffraction. Mechanistic implications of the results are briefly discussed.     

The role of molecular mechanics in the prediction of the chain conformation of polymers in the crystalline state: Syndiotactic polymers

Molecular mechanics methods have been used in order to find the conformations of various syndiotactic polymers in crystals. Three different classes of polymers have been examined: i) polyolefins, such as poly(propylene), polystyrene, poly(1‐butene) and poly(1,2‐butadiene); ii) polydienes, such as cis‐1,4‐poly(1,3‐pentadiene); iii) alternating copolymers of carbon monoxide with styrene or styrene derivatives. The presence of conformational polymorphism in some of the studied polymers is predicted and explained by maps and minimizations of the conformational energy. The calculated internal parameters and chain axis repeats of all the considered polymers result in very good agreement with X‐ray experimental data reported in literature. The role of intramolecular nonbonded interactions in determining the conformations of the polymer chains is thoroughly discussed.     

2-alkyl-1,3-butadiene polymerization under the influence of π-allylic complexes of transition metals

Stereoregulation in the polymerization of 2-alkyl-1,3-butadienes with transition metal π-allylic complexes has been studied. The direction of isoprene polymerization is shown to be a function of the nature of the metal and ligands in the allylic compound. The presence of acidic ligands in π-allylic complexes of Zr, Cr, Mo, and Co contributes to 1,4-addition and increases the selectivity of π-allylic nickel complexes, favoring cis-1,4-structure formation. Investigation of the model reaction of 2-alkyl-1,3-butadienes with bis(π-perdeuterocrotyl nickel iodide) revealed that active sites have an π-allylic type structure. The mechanism of formation of π-allylic adducts and the main factors which determine the dependence of direction and rate of polymerization on the nature of a monomer in the diene series: 2-methyl-1,3-butadiene(isoprene), 2-ethyl-1,3-butadiene, 2-isopropyl-1,3-butadiene, and 2-tert-butyl-1,3-butadiene, are discussed.