Polymerization Of Butadiene Research Articles

Stereoselective Polymerization of Conjugated Dienes and Styrene−Butadiene Copolymerization Promoted by Octahedral Titanium Catalyst

The ability of the dichloro{1,4-dithiabutanediyl-2,2‘-bis(4,6-di-tert-butylphenoxy)}titanium complex (1) to catalyze homopolymerization of conjugated dienes and copolymerization of butadiene with styrene is reported. After proper activation with methylalumoxane, 1 resulted active in the trans-1,4 selective polymerization of butadiene and isoprene with good activity. The molecular weight distributions of the polymers are monomodal with the polydispersity indexes, consistent with a single site behavior of the catalyst. Isotactic polystyrene-co-trans-1,4-polybutadiene with an unprecedented architecture, covering a wide range of compositions (xS = 0.15−0.97), were also obtained. The chemo- and stereoselectivity of butadiene insertion and the isospecific styrene polymerization of the title catalyst are retained when the two monomers are copolymerized. The molecular weight distributions are consistent with the material being copolymeric in nature. The reactivity ratios values and the microstructure analysis (by means of 13C NMR) indicate a random distribution of the two monomers in the polymer chain.

Polymerization of butadiene on a titanium catalyst in formation of a reaction mixture in turbulent flows

Fundamental aspects of the polymerization of butadiene in the presence of a titanium catalyst under intensive agitation of the reaction mixture in the initial stage of polymerization, provided by use of a tubular turbulent divergent-convergent prereactor, were examined.

Regio- and stereochemistry of the first insertion step in the 1,3-butadiene polymerization catalyzed by CpTiCl 3–MAO

CpTiCl 3–MAO (methylaluminoxane) catalytic system promotes the butadiene polymerization leading to 85% of 4,1- cis polymer. The generally well accepted homopolymerization mechanism involves a diene insertion on a π-allylic terminal growing chain. In α-olefin–diene copolymerizations, diene monomer can also insert on a σ carbon–metal bond. In order to simulate an insertion of a conjugated diene on a σ chain, experimental and theoretical studies, relative to the first insertion step, are reported. Unexpectedly 56% of 1,2-primary and 44% of 4,1- trans first inserted units were obtained, by using as catalyst CpTiCl 3/MAO/Al( 13CH 3) 3. The experimental results were rationalized by DFT (Density Functional Theory) calculations, by including a solvent molecule coordinated to the catalytic site during the first insertion step.

Atom transfer radical polymerization of butadiene using MoO2Cl2/PPh3 as the catalyst

AbstractAtom transfer radical polymerization has been used to successfully synthesize polybutadiene. This was achieved by using MoO2Cl2/triphenyl phosphine as the catalyst and the various organic halide compounds such as methyl‐2‐chloropropionate, CCl4, 1,4‐dichloromethyl benzene, 1‐phenylethyl chloride, and benzyl chloride as initiators. The monomer conversion increased up to 50% with polymerization time. The polydispersity indices of the polymers were as high as above 1.5. However, the polymerizations were controlled and the polydispersity indices of the polymers were less than 1.5 throughout the polymerizationin reverse atom transfer radical polymerization. The chemical structure of the polymer obtained was characterized by 1HNMR and FTIR. The valency states of molybdenum in this reactive system were detected by UV–vis spectra. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3517–3522, 2007

The Mechanism of Polymerization of Butadiene by “Ligand-Free” Nickel(II) Complexes

The polymerization of 1,3-dienes has been well-studied using an array of metal-containing complexes. Although a variety of (π-allyl) Ni(II) catalysts have been shown to be active for diene polymeri...

New constrained geometry catalysts-type yttrium, samarium and neodymium derivatives in olefin polymerization

A straightforward synthetic methodology to prepare ansa-monocyclopentadienyl-imino-pyridine dichloro metal derivatives of the type MLCl 2(THF) {M = Y, Sm, Nd} has been developed. Here, we report the syntheses and characterizations of both the ligand and the complexes and the results of some catalytic tests towards olefin polymerization. The most astonishing data come from the influence of both the metal fragments and the co-catalysts used towards the selectivity in butadiene polymerization: in fact, changing these parameters it is possible to range from >99% 1,4 cis-polybutadiene to >99% 1,4 trans-polybutadiene.

Polymerization of 1,3-butadiene with VO(P 204) 2 and VO(P 507) 2 activated by alkylaluminum

The oxovanadium phosphonates (VO(P 204) 2 and VO(P 507) 2) activated by various alkylaluminums (AlR 3, R = Et, i-Bu, n-Oct; HAlR 2, R = Et, i-Bu) were examined in butadiene (Bd) polymerization. Both VO(P 204) 2 and VO(P 507) 2 showed higher activity than those of classical vanadium-based catalysts (e.g. VOCl 3, V(acac) 3). Among the examined catalysts, the VO(P 204) 2/Al(Oct) 3 system (I) revealed the highest catalytic activity, giving the poly(Bd) bearing M n of 3.76 × 10 4 g/mol, and M w/ M n ratio of 2.9, when the [Al]/[V] molar ratio was 4.0 at 40 °C. The polymerization rate for I is of the first order with respect to the concentration of monomer. High thermal stability of I was found, since a fairly good catalytic activity was achieved even at 70 °C (polymer yield > 33%); the M n value and M w/ M n ratio were independent of polymerization temperature in the range of 40–70 °C. By IR and DSC, the poly(Bd)s obtained had high 1,2-unit content (>65%) with atactic configuration. The 1,2-unit content of the polymers obtained by I was nearly unchanged, regardless of variation of reaction conditions, i.e. [Al]/[V], ageing time, and reaction temperature, indicating the high stability of stereospecificity of the active sites.

Distributions of active sites of titanium-containing catalytic system in terms of stereoregulating power and kinetic nonuniformity in butadiene polymerization

The nonuniformity of active sites of a titanium-containing catalytic system in terms of their stereoregulating ability and kinetic activity during butadiene polymerization was studied. It was shown that active sites of three types differing in stereoregulating power and kinetic activity can be formed under polymerization conditions corresponding to the maximum catalyst activity. By solving inverse kinetic problems, the rate parameters for active sites of different types were obtained.

Control of Mechanical Behavior in Polyolefin Composites: Integration of Glassy, Rubbery, and Semicrystalline Components

The mechanical properties of a homologous series of polyolefin block copolymers comprised of glassy poly(cyclohexylethylene) (C), elastomeric poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E) are documented. Monodisperse CPEPC, CPE, and CEPEC with mass fractions wC ∼ 0.39−0.44 and 0 ≤ ξ ≤ 1, where ξ = wE /(wE + wP), were synthesized by sequential anionic polymerization of styrene, isoprene, and butadiene followed by catalytic hydrogenation. These materials hierarchically microphase separate into lamellae, within which templated crystallization-induced segregation occurs. As ξ increases, the unoriented, polydomain CPEPC materials exhibit monotonically increasing elastic moduli and yield stresses, comparable ultimate tensile strengths, and decreasing failure strains. Cold drawing the CPEPC polymers yields high-strength materials, the structures of which are examined by small- and wide-angle X-ray scattering. Drawn CPEPC-70 (ξ = 0.70) exhibits improved toughness with an ultimate tensile strength σfail = 75 ± 10 MPa and elongation at break of εfail = 1.22 ± 0.22, as compared to σfail = 92 ± 21 MPa and εfail = 0.86 ± 0.18 for drawn CEC (ξ = 1.00). Elasticity measurements on the drawn samples demonstrate that materials with ξ > 0 exhibit low degrees of stress softening, while smaller permanent sets and higher failure strains are observed as ξ decreases.

Application of online near infrared spectroscopy to study the kinetics of anionic polymerization of butadiene

Online Fourier-transform near infrared (FT-NIR) spectroscopy in combination with a fiber optic probe was utilized to study the kinetics of the anionic polymerization of butadiene. The conversion of the butadiene to methylene protons in the polymer was monitored in solution polymerization conditions by monitoring the absorbance at 1632 nm. The off-line gel permeation chromatography, GPC, technique was used to validate the online FT-NIR spectroscopy method. Butadiene polymerization kinetics in cyclohexane initiated with n-butyllithium at different initiator concentrations and temperatures was studied. A phenomenological kinetic expression for the anionic polymerization of butadiene in cyclohexane initiated with n-butyllithium was determined. The predictions of the kinetic expression were in agreement with kinetic data reported in the literature.

Modification of Model Ethylene‐Butene Copolymers Using Gamma Radiation and an Organic Peroxide

AbstractWell‐characterized linear ethylene‐butene copolymers with polydispersities lower than 1.1 were modified using gamma radiation and an organic peroxide with the purpose of assessing the relative importance and form of evolution of the chain‐linking processes with these two methods. The copolymers used in this work were obtained by hydrogenation of polybutadienes, which were synthesized by anionic polymerization of butadiene. Part of these materials were irradiated by gamma rays in a 60Co radiation facility and the rest was modified with 2,5‐dimethyl‐2,5 di(terbutyl peroxy)‐hexane in the molten state. As expected, the critical radiation dose and the critical concentration of peroxide required for the onset of gelation decreases with average molecular weight of the original copolymer. Although, the chain‐linking reactions govern the modification process, there is a fraction of molecular chains that suffers scission. The measurable fraction of molecules having molecular weights lower than the original quasi‐monodisperse copolymers is, for both processes, about 5% of the total modified polymer. On the post‐gel region, the gel amount increases continuously with the radiation dose and the peroxide concentration added to the copolymers. For the radiation modified polymers, the calculation of the evolution of the molecular weights assuming ideal network forming conditions agreed very well with the experiments both, before and after the gel point. This is not accomplished when the modification process is done with the use of peroxides. Also, the results obtained from the peroxide modification processes at low relative concentrations with respect to the critical one for gelation show that the evolution of the structural modification evolves at a considerable lower rate than that observed in the radiation results.

Synthesis of new Cr(II) complexes with bidentate phosphine ligands and their behavior in the polymerization of butadiene: Influence of the phosphine bite angle on catalyst activity and stereoselectivity

Some new chromium(II) complexes were synthesized by reacting CrCl 2(thf) with various bidentate phosphines [bis(diphenylphosphino)methane (dppm); 1,2-bis(diphenylphosphino)ethane (dppe); 1,3-bis(diphenylphosphino)propane (dppp); bis(diphenylphosphino)amine (dppa)] and a new family of catalysts for the polymerization of butadiene was prepared by reacting the above chromium complexes with methylaluminoxane (MAO). These systems were found to be in some cases extremely active and they gave predominantly 1,2-polybutadienes (1,2 content >85%) having different tacticity (syndiotactic or predominantly isotactic) depending on the phosphine ligand bonded to the chromium atom. The influence of the type of ligand on catalyst activity and selectivity is discussed.

Interaction of LnCl3 · 6H2O crystal hydrates with the alkoxy derivatives of aluminum in organic solvents

The interaction of LnCl3 · 6H2O (Ln = Pr, Nd, and Tb) with the alkoxy derivatives of aluminum (RO)nAlCl3−n (where R = Et or iso-Bu; n = 1–3) in organic solvents was studied. It was found that the reaction of the crystal water of LnCl3 · 6H2O with (RO)nAlCl3−n resulted in the partial dehydration of the crystal hydrates with the formation of an alcohol (ROH) and the LnCl3 · 3H2O · 3(RO)mAl(OH)Cl2−m complex (m = 1, 2). The solid colloidal particles of this complex and a solvent form a lanthanide-containing gel. The physicochemical (including luminescence) and catalytic properties of the complex in butadiene polymerization and 1,1-gem-dibromo-2-phenylcyclopropane dehalogenation were studied.

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 kinetic study of butadiene polymerization with a cobalt-containing catalyst in hexane

The kinetics of butadiene polymerization in hexane initiated by a catalyst prepared through the interaction of cobalt 2-ethylhexanoate with ethylaluminum sesquichloride and isoprene in the absence of water at Co: Al: isoprene = 1: 20: 20 (mol/mol) has been studied. The reaction orders with respect to the monomer and cobalt ethylhexanoate are estimated as 1.45 ± 0.04 and 1.5 ± 0.3, respectively. The concentration of active centers of the catalyst turns out to be 60 mol % of the cobalt concentration, as determined by the fractional inhibition of polymerization with cyclopentadiene. The rate constant of chain propagation, as calculated from the kinetic data, appears to be 1700 l/(mol min). The effective activation energy is 25.1 ± 7.5 kJ/mol.

Manifold Assembly for the Convenient Polymerization of Ethylene Oxide and Butadiene

Manifold Assembly for the Convenient Polymerization of Ethylene Oxide and Butadiene

Polymerization of butadiene by neodymium catalysts on oxide supports

The suspension polymerization of butadiene in hexane and toluene in the presence of catalysts composed of organoaluminum compounds and neodymium versatate applied on oxides (Al2O3, aluminum silicate A-14, Aerosil A-300, and white soot BS-200) has been studied. Triisobutylaluminum and its combination with ethylaluminum sesquichloride are used as organoaluminum compounds. The activity and stereospecificity of the catalysts has been found to depend strongly on the nature of supports. Catalysts based on Aerosil and white soot appear to be the most active. With the use of these catalysts, polybutadiene containing up to 97.5% 1,4-cis-units has been synthesized.

Viscoelastic behavior of fullerene end-capped linear polymers

Viscoelastic behavior of C 60-end-capped linear polybutadiene and C 60-end-capped poly(butadiene- co-styrene) with molecular weight ( M n) ranging from 30 to 130 kg/mol and with polydispersity index ( M w/ M n) ranging from 1.02 to 1.08 was investigated. These polymers were synthesized through anionic polymerization of butadiene and styrene in hexane, in which the living ends were capped with the C 60 via an alcoholate bridging. Rheological measurements showed that the polymer dynamics in the terminal zone were profoundly affected by the presence of fullerene, while the dynamics in the entanglement-plateau and at the terminal relaxation were nearly unaffected.

Activity and stereospecificity of cobalt-methylaluminoxane catalyst in butadiene polymerization

Butadiene polymerization in aliphatic and aromatic solvents mediated by a preliminarily formed catalyst consisting of cobalt 2-ethylhexanoate, methylaluminoxane, and diene was studied. It was shown that the catalyst was active at a molar ratio of methylaluminoxane: cobalt: diene = 75−200:1:20, yielding high-molecular-mass polymers (intrinsic viscosity, 1.8–2.7 dl/g) containing at least 98% cis-1,4-units. Preliminary formation of the catalyst was found to increase its activity in butadiene polymerization at a low Al:Co ratio. In this case, the catalyst retains its high stereospecificity (the amount of cis-1,4-units in the polymer reaches 98% and more) independently of the nature of the solvent used for polymerization.

Comparison of the Solvents n‐Hexane, tert‐Butyl Benzene and Toluene in the Polymerization of 1,3‐Butadiene with the Ziegler Catalyst System Neodymium Versatate/Diisobutylaluminum Hydride/Ethylaluminum Sesquichloride

The influence of the solvents n‐hexane, tert‐butyl benzene (TBB) and toluene on the Nd‐catalyzed polymerization of butadiene was studied. Special emphasis was placed on polymerization kinetics and on the evolution of molar masses and molar mass distributions with monomer conversion. Distinct differences were found between the three solvents. From the polymerization kinetics there is evidence which supports Porri's view on the competitive coordination between aromatic solvents and butadiene to active Nd‐sites. In addition, there are indications for the irreversible transfer of benzyl‐H‐atoms from toluene to active allyl‐anionic polymer chains. The evolution of molar mass distributions with monomer conversion provides evidence for the existence of two active catalyst species which are present in all three solvents. One of these two species is highly reactive (“hot”) and short‐lived. This species generates BR with high molar mass. The second species has a low reactivity and lives throughout the entire course of the polymerization. In n‐hexane the “hot”, short‐lived species is present only at the start of the polymerization, whereas in TBB and toluene, the short‐lived species becomes evident at monomer conversion>10% and is constantly (re)generated. Cis‐1,4‐contents determined at final monomer conversion are not in line with other available studies in this field.