Copolymerization of 2‐butene and ethylene with catalysts based on titanium and zirconium complexes

The polymerization of 2‐butene and its copolymerization with ethylene have been investigated using four kinds of dichlorobis(β‐diketonato)titanium complexes, [ArN(CH₂)₃NAr]TiCl₂ (Ar = 2,6‐ⁱPr₂C₆H₃) and typical metallocene catalysts. The obtained copolymers display lower melting points than those produced of homopolyethylene under the same polymerization conditions. ¹³C NMR analysis indicates that 9.3 mol‐% of 2‐butene units were incorporated into the polymer chains with Ti(BFA)₂Cl₂‐MAO as the catalyst system. With the trans‐2‐butene a higher copolymerization rate was observed than with cis‐2‐butene. A highly regioselective catalyst system for propene polymerization, [ArN(CH₂)₃NAr]TiCl₂ complex using a mixture of triisobutylaluminium and Ph₃CB(C₆F₅)₄ as cocatalyst, was found to copolymerize a mixture of 1‐butene and trans‐2‐butene with ethylene up to 3.1 mol‐%. Monomer isomerization‐polymerization proceeds with typical metallocene catalysts to produce copolymers consisting of ethylene and 1‐butene.     

Kinetics and mechanism of metallocene‐catalyzed olefin polymerization: Comparison of ethylene,propylene homopolymerizations,and their copolymerization

A series of ethylene, propylene homopolymerizations, and ethylene/propylene copolymerization catalyzed with rac‐Et(Ind)₂ZrCl₂/modified methylaluminoxane (MMAO) were conducted under the same conditions for different duration ranging from 2.5 to 30 min, and quenched with 2‐thiophenecarbonyl chloride to label a 2‐thiophenecarbonyl on each propagation chain end. The change of active center ratio ([C^*]/[Zr]) with polymerization time in each polymerization system was determined. Changes of polymerization rate, molecular weight, isotacticity (for propylene homopolymerization) and copolymer composition with time were also studied. [C^*]/[Zr] strongly depended on type of monomer, with the propylene homopolymerization system presented much lower [C^*]/[Zr] (ca. 25%) than the ethylene homopolymerization and ethylene–propylene copolymerization systems. In the copolymerization system, [C^*]/[Zr] increased continuously in the reaction process until a maximum value of 98.7% was reached, which was much higher than the maximum [C^*]/[Zr] of ethylene homopolymerization (ca. 70%). The chain propagation rate constant (k_p) of propylene polymerization is very close to that of ethylene polymerization, but the propylene insertion rate constant is much smaller than the ethylene insertion rate constant in the copolymerization system, meaning that the active centers in the homopolymerization system are different from those in the copolymerization system. Ethylene insertion rate constant in the copolymerization system was much higher than that in the ethylene homopolymerization in the first 10 min of reaction. A mechanistic model was proposed to explain the observed activation of ethylene polymerization by propylene addition. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 867–875     

Radiation-induced copolymerization of methyl trifluoroacrylate with ethylene

Copolymerization of methyl trifluoroacrylate (MTFA) with ethylene in bulk was induced by γ irradiation. The copolymerization was observed to proceed in the liquid monomer mixture of MTFA and ethylene at 25°C with the dose rates ranging from 5.0 × 10⁴ to 1.0 × 10⁶ rad/hr. A wide range of the initial monomer composition gives an almost equimolar and alternating copolymer. The highest polymerization rate was observed at the equimolar monomer composition. The dose rate exponent of the polymerization rate is unity. The reactivity ratios of r₁ (MTFA) and r₂ (ethylene) were determined to be 0.034 and 0.14, respectively.     

Alternating copolymerization of ethylene and 1-octene with meso-[dimethylsilylbis(2-methyl-1-indenyl)]zirconium dichloride-methylaluminoxane as catalyst system

Copolymerizations of ethylene and α-olefins with homogeneous metallocene catalysts generally give the corresponding random copolymers with narrow molecular mass distributions. In this study, we have conducted the copolymerization of ethylene and 1-octene with the meso-Me₂Si(2-Me-1-Ind)₂ZrCl₂-methylaluminoxane (MAO) catalyst system, and analyzed the microstructure of the resulting copolymers in detail. The content of the alternating [EO] sequence increases markedly with an increase in the feed ratio of 1-octene to ethylene, reaching over 95% under appropriate copolymerization conditions. We have thus succeeded in preparing the first sample of alternating olefin copolymers.     

Facile,efficient functionalization of polyethylene via regioselective copolymerization of ethylene with cyclic dienes

The copolymerizations of ethylene with cyclic dienes [dicyclopentadiene (DCPD) and 2,5‐norbornadiene (NBD)] using bis(β‐enaminoketonato)titanium complexes [PhN = C(R₂)CHC(R₁)O]₂TiCl₂ ( 1a : R₁ = CF₃, R₂ = CH₃; 1b : R₁ = t‐Bu, R₂ = CF₃; 1c : R₁ = Ph, R₂ = CF₃) have been investigated. In the presence of modified methylaluminoxane, these complexes exhibited high catalytic activities in the copolymerization of ethylene with DCPD or NBD, affording high molecular weight copolymers with unimodal molecular weight distributions. ¹H and ¹³C‐NMR spectra reveal ethylene/DCPD copolymerizations by catalysts 1a – c proceeds through the enchainment of norbornene ring. Catalysts 1a and 1c showed a tendency to afford alternating copolymers. More noticeably, catalysts 1b and 1c bearing bulky substituents on the ligands promote ethylene/NBD copolymerization without crosslinking, affording the copolymer containing intracyclic double bonds. The NBD incorporation as high as 27.2 mol % has been achieved by catalyst 1c . Moreover, the microstructures of the copolymers were further confirmed by the measurement of reactivity ratios and dyad monomer sequences as well as mean sequence lengths. The intracyclic double bonds of ethylene/DCPD or ethylene/NBD copolymers can be fully converted into polar groups such as epoxy, amine, silane, and hydroxyl groups under mild conditions. Convenient synthesis of hydroxylated polyethylene can be provided for the first time through the ring opening reaction of epoxide. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1764–1772, 2010     

Synthesis of ethylene/propylene elastomers containing a terminal reactive group: The combination of metallocene catalysis and control chain transfer reaction

This article discusses a chemical route to prepare new ethylene/propylene copolymers (EP) containing a terminal reactive group, such as ?‐CH₃ and OH. The chemistry involves metallocene‐mediated ethylene/propylene copolymerization in the presence of a consecutive chain transfer agent—a mixture of hydrogen and styrene derivatives carrying a CH₃ (p‐MS) or a silane‐protected OH (St‐OSi). The major challenge is to find suitable reaction conditions that can simultaneously carry out effective ethylene/propylene copolymerization and incorporation of the styrenic molecule (St‐f) at the polymer chain end, in other words, altering the St‐f incorporation mode from copolymerization to chain transfer. A systematic study was conducted to examine several metallocene catalyst systems and reaction conditions. Both [(C₅Me₄)SiMe₂N(^t‐Bu)]TiCl₂ and rac‐Et(Ind)₂ZrCl₂, under certain H₂ pressures, were found to be suitable catalyst systems to perform the combined task. A broad range of St‐f terminated EP copolymers (EP‐t‐p‐MS and EP‐t‐St‐OH), with various compositions and molecular weights, have been prepared with polymer molecular weight inversely proportional to the molar ratio of [St‐f]/[monomer]. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1858–1872, 2005     

Radiation induced copolymerization of chlorotrifluoro ethylene with butenes

The radiation induced copolymerization of chlorotrifluoro ethylene (CTFE) with various butenes was studied at temperatures between ?20°C and +40°C using ⁶⁰Co-γ rays. In the case of isobutene (IB) an almost alternating crystalline copolymer is formed in a heterogeneous reaction. At high IB-concentrations a cationic homopolymerization of this olefin occurs simultaneously to the radical copolymerization. The copolymerization rate increases with increasing temperature and degree of conversion. The highest rates are obtained for monomer mixtures with about 80 to 90 mole % CTFE. The decrease in rate for monomer mixtures with still higher CTFE concentrations is assumed to be partly due to the low IB-concentration and partly to degradative chain transfer by the isobutene. In support of this assumption molecular weights and melting points of the copolymer have been determined. Similar results were obtained for butene-1 but in this case, no cationic homopolymerization was observed and the reaction proceeded homogeneously. Cis- and trans-butene-2 only acted as polymerization inhibitors.     

Copolymerization of ethylene with styrene catalyzed by a linked bis(phenolato) titanium catalyst

Copolymerization of ethylene with styrene, catalyzed by 1,4‐dithiabutanediyl‐linked bis(phenolato) titanium complex and methylaluminoxane, produced exclusively ethylene–styrene copolymers with high activity. Copolymerization parameters were calculated to be r_E = 1.2 for ethylene and r_S = 0.031 for styrene, with r_E r_S = 0.037 indicating preference for alternating copolymerization. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with styrene content up to 68%. The copolymer microstructure was fully elucidated by ¹³C NMR spectroscopy revealing, in the copolymers with styrene content higher than 50%, the presence of long styrene–styrene homosequences, occasionally interrupted by isolated ethylene units. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1908–1913, 2006     

Catalytic syntheses of alternating, stereoregular ethylene/cycloolefin copolymers

The alternating stereospecific copolymerization of ethylene with cycloolefins (cyclopentene, cycloheptene, and cyclooctene) has been investigated with a series of constrained geometry titanium catalysts (CGCs). The metallocene IndSiMe₂(^tBuN)TiCl₂ was found to generate highly alternating and stereoregular cycloolefin-co-ethylene polymers while Me₄CpSiMe₂(^tBuN)TiCl₂ produced alternating atactic polymers. In addition, novel Ti-complexes of the general formula benz[6.7]indenylSiMe₂(^tBuN)TiMe₂ were synthesized and fully characterized. The chiral indenyl Ti complexes were found to produce exclusive 1,2-enchainment of the cycloolefin to generate highly stereoregular and alternating copolymers.     

Living copolymerization of ethylene with norbornene by fluorinated enolato‐imine titanium catalyst

Complex [Ti(κ²‐N,O‐{2,6‐F₂C₆H₃N?C(Me)C(H) ?C(CF₃) O})₂Cl₂] ( 1 ) was evaluated as catalyst for living copolymerization of ethylene (E) with norbornene (N) upon activation with dried methylaluminoxane (d‐MAO) at temperatures between 25 and 90 °C. Copolymerization performed at different [N]/[E] feed ratios afforded stereoirregular alternating high molar mass P(E‐co‐N) with narrow molar mass distribution. The living nature of E‐co‐N copolymerization by 1 /d‐MAO was demonstrated by kinetics at 50 °C. This catalyst system was used for the synthesis of block copolymers such as polyethylene (PE)‐block‐P(E‐co‐N) with a crystalline PE block and an amorphous P(E‐co‐N) block as well as P(E‐co‐N)₁‐block‐P(E‐co‐N)₂, having different norbornene contents in the segments and thus having different T_g values. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Alternating Copolymerization of Ethylene and 5‐Hexen‐1‐ol with [Ethylene(1‐indenyl)(9‐fluorenyl)]‐zirconium Dichloride/Methylaluminoxane as the Catalyst

The copolymerization of ethylene and 5‐hexen‐1‐ol pretreated with trimethylaluminium was performed using [ethylene(1‐indenyl)(9‐fluorenyl)]zirconium dichloride/methylaluminoxane as the catalyst. The 5‐hexen‐1‐ol unit in the copolymer could be increased to about 50 mol‐% with increasing [5‐hexen‐1‐ol/ethylene[ ratio. ¹³C NMR analysis proved that the poly(ethylene‐co‐(5‐hexen‐1‐ol)) containing 50 mol‐% of 5‐hexen‐1‐ol units is an almost alternating copolymer.     

Alternating stereospecific copolymerization of ethylene and propylene with metallocene catalysts

The copolymerization of ethylene and propylene with bridged metallocenes Me(2)E(3-RCp)(Flu)X(2)/MAO (E = C, X = Me; E = Si, X = Cl; R = H or alkyl) was investigated. Ethylene/propylene copolymerization with metallocenes having heterotopic active sites (R =Me, i-Pr) yield alternating, isotactic ethylene/propylene copolymers with percentages of alternating EPE+PEP triads in the range of 61-76% at 50% ethylene incorporation. Both the nature of the substituent R and the bridge E influence the copolymerization behavior including the copolymerization activity, copolymer sequence distribution, molecular weight, and stereochemistry. Silicon-bridged metallocenes produce copolymers with higher activity and molecular weight but lower propylene incorporation at similar feeds than the carbon-bridged analogues. Isotactic PEPEP sequences were observed for all metallocenes, while the tacticities of the EPPE sequences varied with the bridge and the substituent on the metallocene ligand. Isotactic PEPEP sequences and atactic EPPE sequence errors in the alternating copolymers are consistent with a mechanism where the comonomers are enchained alternately at the heterotopic coordination sites of the metallocenes. Isotactic EPPE sequences are indicative of occasional multiple insertions at the stereospecific site, caused by an isomerization of the chain prior to monomer insertion (backskip).     

Alternating copolymerization of ethylene with maleic anhydride

The copolymerization of ethylene with maleic anhydride was carried out with γ-radiation and a radical initiator, i.e., 2,2′-azobisisobutyronitrile and diisopropyl peroxydicarbonate under pressure at various reaction conditions. The homopolymerization of neither monomer was observed in this system. In the γ-ray-initiated copolymerization the G value (polymerized monomer molecules per 100 e.v.) was shown to be between 10³ and 10⁴. It was found that the dose rate exponent of the rate is approximately unity, and the rate is proportional to the amount of ethylene monomer. Apparent activation energies of 1.8 and 27.5 kcal./mole were obtained for γ-ray-initiated and AIBN-initiated copolymerization, respectively. Since the composition of copolymer is independent of monomer molar ratio and the molar ratio of ethylene to maleic anhydride in the polymer is approximately unity, the monomer reactivity ratios were obtained as r_E ? 0 and r_M ? 0 for γ-ray-initiated polymerization at 40°C. Alternating copolymerization was, therefore, concluded to occur. Infrared analysis of the copolymer is almost consistent with this. The copolymer in the solid state is amorphous. It is soluble in water, cyclohexane, and dimethylformamide and insoluble in lower alcohols, ether, and aromatic hydrocarbons. The aqueous solution of polymer gave a strong acid.     

Stereoregular and Bernoullian copolymerization of styrene and ethylene by bridged metallocene catalysts

A stereoregular and Bernoullian copolymer of styrene and ethylene was produced by the catalyst system of rac-[isopropylidenebis(1-indenyl)]zirconium dichloride and MAO. This catalyst system yields a high molecular weight copolymer with good activity at 50°C. The copolymer consists of Et-Et, St-Et, and head to tail St-St sequences and has a highly isotactic Et-St alternating sequence. This copolymer shows a melting point (80 – 110°C), due to the isotactic alternating sequence.     

Copolymerization of ethylene and 1-butene using a Cr—silica catalyst in a slurry reactor

A novel slurry reactor was used to investigate the copolymerization behavior of ethylene and 1-butene in the presence of 1 wt % Cr on Davison silica (Phillips-type) catalyst over the temperature range of 0–50°C, space velocity of about 0.0051 [m³ (STP)]/(g of catalyst) h, and a fixed ethylene to 1-butene feed mole ratio of 95 : 5. The effect of varying the ethylene to 1-butene feed ratios, 100 : 0, 96.5 : 3.5, 95 : 5, 93 : 7, 90 : 10, 80 : 20, and 0 : 100 mol/mol at 50°C was also studied. The addition of 1-butene to ethylene typically increased both copolymerization rates and yields relative to ethylene homopolymerization with the same catalyst, reaching a maximum yield for an ethylene: 1-butene feed ratio of 95 : 5 at 50°C. The incorporation of 1-butene within the copolymer in all cases was less than 5 mol %. The average activation energy for the apparent reaction rate constant, k_a, based on total comonomer mole fraction in the slurry liquid for the ethylene to 1-butene feed mole ratio of 95 : 5 in the temperature range of 50–30°C measured 54.2 kJ/mol. The behavior for temperatures between 30 to 0°C differed with an activation energy of 98.2 kJ/mol; thus, some diffusion limitation likely influences the copolymerization rates at temperatures above 30°C. A kinetics analysis of the experimental data at 50°C for different ethylene to 1-butene feed ratios gave the values of the reactivity ratios, r₁ = 27.3 ± 3.6 and r₂ ≅ 0, for ethylene and 1-butene, respectively. © 1996 John Wiley & Sons, Inc.     

Alternating,gradient, block,and block–gradient copolymers of ethylene and norbornene by Pd–Diimine‐Catalyzed “living” copolymerization

We demonstrate, in this article, the facile synthesis of a broad class of low‐polydispersity ethylene–norbornene (E–NB) copolymers having various controllable comonomer composition distributions, including gradient, alternating, diblock, triblock, and block–gradient, through “living”/quasiliving E–NB copolymerization facilitated with a single Pd – diimine catalyst ( 1 ). This synthesis benefits from two remarkable features of catalyst 1 , its high capability in NB incorporation and high versatility in rendering E–NB “living” copolymerization at various NB feed concentrations ([NB]₀) while under an ethylene pressure of 1 atm and at 15 °C. At higher [NB]₀ values between 0.42 and 0.64 M, E–NB copolymerization with 1 renders nearly perfect alternating copolymers. At lower [NB]₀ values (0.11–0.22 M), gradient copolymers yield due to gradual reduction in NB concentration, with the starting chain end containing primarily alternating segments and the finishing end being hyperbranched polyethylene segments. Through two‐stage or three‐stage “living” copolymerization with sequential NB feeding, diblock or triblock copolymers containing gradient block(s) have been designed. This work thus greatly expands the family of E–NB copolymers. All the copolymers have controllable molecular weight and relatively low polydispersity (with polydispersity index below 1.20). Most notably, some of the gradient and block–gradient copolymers have been found to exhibit the characteristic broad glass transitions as a result of their possession of broad composition distribution. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Copolymerization of n‐butylacrylate with methylmethacrylate by a novel photoinitiator, 1‐(bromoacetyl)pyrene

The photopolymerization efficiency of pyrene (Py), 1‐acetylpyrene (AP), and 1‐(bromoacetyl)pyrene (BP) for copolymerization of n‐butylacrylate (BA) with methylmethacrylate (MMA) was compared. A kinetic study of solution copolymerization in DMSO at 30 ± 0.2°C showed that the Py could not initiate copolymerization even after 20 h, whereas with AP as initiator, less than 1% conversion was observed. However, introduction of a Br in α‐methyl group of AP significantly enhanced the percent conversion. The kinetics and mechanism of copolymerization of BA with MMA using BP as photoinitiator have been studied in detail. The system follows nonideal kinetics (R_p α [BP]^0.67[BA]¹[MMA]^0.98), and degradative solvent transfer reasonably explains these kinetic nonidealities. The monomer reactivity ratios (MRRs) of MMA and BA have been estimated by the Finemann–Ross and Kelen–Tudos methods, by analyzing copolymer compositions determined by ¹H‐NMR spectra. The values of r₁ (MMA) and r₂ (BA) were found to be 2.17 and 0.44, respectively, which suggested the high concentration of alternating sequences in the random copolymers obtained. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 261–267, 2007     

Copolymerization of ethylene/carbon monoxide by a cationic hydridoaquopalladium complex

The cationic hydridoaquopalladium (II) complex, trans-[(PCy₃)₂Pd(H)(H₂O)]⁺BF^?₄, is an excellent catalyst for the ethylene/carbon monoxide alternating copolymerization in the presence of a bidentate phosphorus ligand and p-toluenesulphonic acid. © 1995 John Wiley & Sons, Inc.     

Influences of steric bulkiness in hydrotris(pyrazolyl)borate ligands on ethylene polymerization reaction

Manganese(II) complex catalysts with hydrotris(pyrazolyl)borate ligands have been examined on their catalytic performance in ethylene polymerization and ethylene/1‐hexene copolymerization. The activities of [Mn(L6)(Cl)(NCMe)] ( 1 ) and [Mn(L10)(Cl)] ( 2 ) activated by Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] for ethylene polymerization go up to 326 and 11 kg mol (cat^?1) h^?1, respectively, (L6^? = hydrotris(3‐phenyl‐5‐methyl‐1‐pyrazolyl)borate anion, L10^? = hydrotris(3‐adamantyl‐5‐isopropyl‐1‐pyrazolyl)borate anion). In particular, for ethylene/1‐hexene copolymerization, complex 1 gives high‐molecular‐weight poly(ethylene‐co‐1‐hexene)s with the highest M_w of 439,000 in manganese olefin polymerization catalyst systems. Moreover, the 1‐hexene incorporation by complex 1 seems more efficient than that by [Mn(L3)(Cl)] ( 4 ) (L3^? = hydrotris(3‐tertiary butyl‐5‐isopropyl‐1‐pyrazolyl)borate anion). In this work, we demonstrated that the coordination geometry and coordination number are also important factors for ethylene polymerization reaction as well as steric hindrances and ligand frameworks in our manganese(II) catalysts. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5720–5727, 2009     

Synthesis of functional star‐shaped poly(ethylene oxide) using the macromonomer technique

Functional poly(ethylene oxide) stars were prepared by free‐radical copolymerization of poly(ethylene oxide) macromonomers with divinylbenzene in water. The poly(ethylene oxide) arm was prepared by anionic polymerization using 2‐[2‐(N,N‐dimethylamino)ethoxy]ethanol potassium alkoxide as the initiator. These functional stars were converted into peripherally charged stars by quaternization of the peripheral tertiary amino groups with methyl iodide.