Copolymerization of 1,3-butadiene and styrene with a neodymium catalyst

Homo- and copolymerization of butadiene and styrene in the presence of the catalyst system Nd(octanoate)₃/CCl₄/Al(iBu)₃ (iBu: isobutyl) were investigated at 60°C in heptane as solvent. The initiating catalyst system is very effective in the polymerization of butadiene. However, the presented copolymerization of butadiene and styrene is only practicable when using a special addition order of the catalyst components and a prescribed ageing phase. Copolymers obtained from various monomer feed ratios were characterized by ¹H and ¹³C NMR spectroscopy and gel-permeation chromatography (GPC). The copolymer characteristics especially microstructure, molar mass and molar-mass distribution (MMD) are strongly dependent on the composition of the monomer mixture.     

Reactions of ozone with olefins: Ethylene,allene, 1,3-butadiene,and trans- 1,3-pentadiene

The reactions of O₃ with ethylene, allene, 1,3-butadiene, and trans-1,3-pentadiene have been studied in the presence of excess O₂ over the temperature range 232 to 298 K. The initial O₃ pressure was varied from 4–18 mtorr, and the olefin pressure was varied from 0.1 to 4.5 torr (ethylene), 2.8 to 39.6 torr (allene), 52.7 to 600 mtorr (1,3-butadiene) or 26.2 to 106 mtorr (trans-1,3-pentadiene). The O₃ decay was monitored by ultraviolet absorption. The reactions are first order in both O₃ and olefin, and the rate coefficients are independent of the O₂ pressure. For the O₃-ethylene system, various diluent gases (O₂, N₂, air) were used and the rate coefficients were found to be independent of the nature of the diluent gas. The various rate coefficients fit the Arrhenius expressions (k in cm³ s^?1): where the reported uncertainties are one standard deviation and R is in cal/mol K.     

Copolymerization of styrene with (Z)-1,3-pentadiene in the presence of a syndiotactic-specific catalyst

Copolymerization of styrene with (Z)-1,3-pentadiene affords copolymers mostly containing 1,2 pentadiene units. Both the styrene and the pentadiene units are in syndiotactic arrangement but the comonomer sequence distribution is far from bernoullian. Interestingly, the behavior of (Z)-1,3-pentadiene does not change much when polymerization temperature raises from −20 to +20°C, notwithstanding that (Z)-1,3-pentadiene affords a 1,2-syndiotactic homopolymer at −20°C but a prevailingly 1,4 cis homopolymer at +20°C. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2697–2702, 1997     

Polymerization of 1,3-butadiene on cobalt and nickel halides

Butadiene polymerizes to cis-1,4 polymer on irregularly stacked, halogen-deficient crystals of cobalt(II) or nickel(II) halides. Halogen is removed from the halides by heating the salts under high vacuum or by photolyzing them in the presence of butadiene. Intrinsic viscosity and solubility of the polymer reach a steady state during polymerization. Cobalt chloride produces polymer of higher intrinsic viscosity than nickel chloride, but polymerization on nickel chloride is faster. Catalytic activity is attributed to the presence of ≤0.1% of nickel and cobalt monohalides in the catalyst.     

Assignments of the vibrational spectra of 2,5-dimethyl-2,4-hexadiene, 4-methyl-1,3-pentadiene and (E)-2-methyl-1,3-pentadiene. Effect of the terminal and lateral methyl groups

The complete assignment of the vibrational spectra of 2,5-dimethyl-2,4-hexadiene, 4-methyl-1,3-pentadiene and (E)-2-methyl-1,3-pentadiene was obtained from a comparative analysis of their i.r. and Raman spectra (solid, liquid and gas) in the range 3200-50 cm⁻¹. It is shown that particular vibrational motions strongly interact to give rise to very characteristic modes depending on the site of methyl substitution. The comparison of our results with those of analogous shorter and larger polyenes and polyenals allows us to discuss the various local coupled motions characteristic of unsubstituted (CHCH CH)CH and methyl substituted (CHC(CH₃)CH), ((CH₃)₂CCH) or (CH₃CHCH) fragments in polyenic chains.     

Chemoselectivity in 4-methyl-1,3-pentadiene polymerization in the presence of homogeneous Ti-based catalysts

The homogeneous catalyst CpTiCl₃-MAO is able to produce a random copolymer of 4-methyl-1,3-pentadiene with ethylene. ¹³C NMR analysis of the copolymers shows that after insertion of ethylene units, the next 4-ymethyl-1,3-pentadiene unit can be inserted in either 1,2 or 1,4 arrangement. The high chemoselectivity observed in the 1,2-syndiotactic homopolymerization of 4-methyl-1,3-pentadiene with respect to the lower one observed in the copolymerization with ethylene is attributed to a back-biting coordination to the Ti of the active species of the penultimate monomer unit of the growing chain.     

Comparison of catalytic properties of systems based on nickel complexes with 1,4-diaza-1,3-butadiene ligands in reactions of styrene hydrogenation and ethylene polymerization

Turnover frequencies of catalytic systems based on nickel complexes with 1,4-diaza-1,3-butadiene (α-diimine) ligands in the reactions of styrene hydrogenation and ethylene polymerization were determined. Results are presented of a study by the electron paramagnetic resonance method and IR spectroscopy of 1,4-diaza-1,3-butadiene complexes of nickel(II) and anion radicals formed in the interaction of the starting components under the conditions of catalysis. It was shown that the paramagnetic Ni(I) complexes are precursors of complexes catalytically active in the hydrogenation and polymerization reactions.     

Copolymerization of 4-methyl-1,3-dioxene-4 with maleic anhydride and terpolymerization with styrene as the third component

Copolymerization of 4-methyl-1,3-dioxene-4 with maleic anhydride was carried out. The monomer reactivity ratio was determined to be r₁ = 0.18, r₂ ～ 0 in terminal model and r₁ = 0.015, r₁′ = 0.224, r₂′ = r₂′ = 0 in the penultimate model. Calculations of run number, linkage probabilities, and number-average chain length in the terminal model and comparison of n (mole ratio of each monomer unit content in copolymer) in each model with the experimental value was made. From these results, the obtained polymer was confirmed to be alternating. Terpolymerization of 4-methyl-1,3-dioxene-4 with maleic anhydride and styrene was also carried out. The agreement of the experimental value (titration by indicator or electroconductivity) of maleic anhydride content with the theoretical value confirms that the terpolymer has a DMS triad sequence.     

Polymerizations of ethylene and styrene initiated with trisiloxane-bridged dinuclear titanium metallocene/MMAO catalyst systems

Two kinds of the trisiloxane-bridged dinuclear titanium metallocene-type complexes were synthesized. They are monocyclopentadienyl and biscyclopentadienyl dinuclear titanocenes with trisiloxane bridges. The above complexes with modified methylaluminoxane (MMAO) cocatalyst initiate the polymerizations of ethylene and styrene to produce high-density polyethylene and syndiotactic polystyrene. In addition, a copolymer of ethylene and styrene was obtained.     

Diels-Alder reaction of 1,3-butadiene derivatives with 1-methyl-2(1H)-quinolones having an electron-withdrawing group at the 4-position.

Diels-Alder reactions of 1-methyl-2(1H)-quinolones having an electron-withdrawing group at the 4-position with isoprene, butadiene sulfone, and cyclohexadiene were performed to yield functionalized phenanthridones stereoselectively at atmospheric and at high pressure. Regioselectivity and stereochemistry of a methoxycarbonyl group were studied using the semi-empirical and ab initio MO methods, respectively.     

Block copolymerization of allene derivatives with 1,3-butadiene by living coordination polymerization with π-allylnickel catalyst

The block copolymerization of allene derivatives (3A–3D) with 1,3-butadiene (2) by [(allyl)NiOCOCF₃]₂ (1) is described. For instance, the living coordination polymerization of phenylallene (3A, 50 equiv) starting from the living poly(2), which was prepared by the polymerization of 2 (160 equiv) by 1, successfully gave a block copolymer of 2 and 3A in high yield. The molecular weight of the block copolymer (4A) in gel permeation chromatography shifted clearly to the higher molecular weight region and kept a unimodal distribution (M_n = 17,400, M_w/M_n = 1.23) in comparison with that of the starting living poly(2) (M_n = 5,600, M_w/M_n = 1.67). The ratio of each segment and the molecular weight of the resulting copolymers could be controlled by the feed ratio of each monomer. The block copolymerization also proceeded successfully by the inverse order of the monomer feeding (i.e., the polymerization of 3A followed by that of 2) to obtain the corresponding block copolymers in high yields. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3916–3921, 1999     

Conformational sensitivity of tetraphenyl-1,3-butadiene derivatives with aggregation-induced emission characteristics

Organic dyes with conformational sensitivity can be used to probe weak interactions at the molecular level. Here, three molecules based on tetraphenyl-1,3-butadienes(TPBs) were synthesized and studied with respect to their synthesis, structural characterization and potential application. All TPBs showed aggregation-induced emission(AIE) characteristics and sensitive conformational properties, in which the emission wavelengths could be changed in different states. The TPBs single crystals revealed that the phenyl groups at the 4-position of the 1,3-butadienes contributed to their conformational sensitivity. Furthermore, the potential application for monitoring the interactions among polyelectrolyte complexes and metal ions was explored, and the results showed that TPBs could be used for sensitively probing some weak interactions by changing the emission wavelengths due to their conformation-sensitive properties. TPBs may become a new star in AIE research fields.     

Polymerization of styrene with chromium acetylacetonate–triisobutylaluminum catalyst system

Styrene is polymerized with chromium acetylacetonate–triisobutylaluminum catalyst at 40°C in a benzene medium. At the stoichiometric ratio of Al/Cr of 4, the activity for polymerization was found to be maximum. Further, the kinetic studies were carried out at this ratio of Al/Cr of maximum activity. The kinetics of polymerization and the total activation energy around 10.00 kcal/mole suggest a coordinate anionic mechanism.     

Polymerization and copolymerization of 2-phthalimidomethyll 1,3-butadiene. II. Kinetic study of the polymerization of 1,3-butadiene and of the copolymerization of 1,3-butadiene with 2-phthalimidomethyl 1,3-butadiene initiated by bis-(η3-allyl nickel trifluoroacetate)

The kinetics of the polymerization of 1,3-butadiene initiated by bis(η³-allyl nickel trifluoroacetate) prepared in benzene was studied in methylene chloride at 40°C. The reaction is first order with respect to the monomer, second order with respect to the catalyst in contrast to the case in which solvent is benzene. We have shown that the presence of a polar molecule (fe, N-methyl phthalimide) decreases the overall rate of polymerization. The apparent reactivity ratios for the system 2-phthalimidomethyl 1,3-butadiene (1)-1,3-butadiene (2) are r₁ = 0.65 ± 0.006 and r₂ = 0.48 ± 0.015.     

Polymerization of 1,3-butadiene under the action of cobalt catalyst in an aliphatic solvent with formation of polymers suitable for commercial use

Polymerization of 1,3-butadiene in an n-hexane solution in the presence of the catalyltic complex cobalt 2-ethylhexanoate-diisobutylaluminum chloride-water-isoprene was studied. The conditions were found for preparing cis-polybutadiene with the molecular-weight distributions ensuring the physicomechanical parameters required for commercial applications.