Copolymerization behavior of Cp2ZrCl2/MAO and [(CO)5WC(Me)OZrCp2Cl]/MAO: a comparative study on ethylene/1-pentene copolymers

Ethylene/1-pentene copolymers were synthesized using Cp₂ZrCl₂(1)/MAO and [(CO)₅WC(Me)OZr(Cp)₂Cl](2)/MAO catalyst systems. The copolymers were characterized by SEC, DSC, FTIR and ¹³C NMR spectroscopy. The copolymers synthesized with [(CO)₅WC(Me)OZr(Cp)₂Cl](2)/MAO had higher average molecular weights and broader polydispersities compared to those produced with Cp₂ZrCl₂(1)/MAO. The chemical heterogeneity was investigated by SEC-FTIR and fractionation techniques. All copolymers showed a higher incorporation of the 1-pentene in the low molecular weight fraction as revealed by SEC-FTIR. Crystallization analysis fractionation (CRYSTAF) showed a broad chemical composition distribution (CCD) for all the copolymers synthesized with these two catalyst systems. Selected copolymers were also analyzed using an automated preparative molecular weight fractionation.     

The effect of the ethylene pressure on its reaction with 1-hexene, 1-octene and 4-methyl-1-pentene

Summary Copolymers of ethylene and 1-hexexe, 1-octene and 4-methyl-1-pentene were obtained using Et[In]₂ZrCl₂/MAO catalyst at various pressures. The increase of 1-hexene and 1-octene concentration in the feed increases catalyst activity(g/nZr.h.bar) and productivity(g/nZr.h). For 4-methyl-1-pentene the activity is independent on comonomer concentration. Increasing the ethylene pressure the productivity of the copolymerization increases and the activity shows a weak decay. Characterization of the copolymer shows that at higher pressure the cristallinity of the copolymers is higher due to lower comonomer incorporation. There is a good linear correlation of cristallinity with comonomer concentration in the feed for 1-hexene and 1-octene at a fixed pressure, but not for 4-methyl-1-pentene.     

Oligomerisation of 1-pentene with metallocene catalysts

The homo-oligomerisation of 1-pentene in the presence of various bridged and non-bridged metallocenes and methylaluminoxane (MAO) at room temperature and at 60°C, respectively, has been studied. The use of the bridged catalysts rac-[C₂H₄(Ind)₂]ZrCl₂ ( 1 ) and [(CH₃)₂Si(Ind)₂]ZrCl₂ ( 2 ) leads to the formation of isotactic poly(1-pentene). The use of Cp₂ZrCl₂ ( 3 ), Cp₂HfCl₂ ( 4 ) and [(CH₃)₅C₅]₂ZrCl₂ ( 5 ) leads to the formation of atactic poly(1-pentene). The stereoregularity of the isotactic poly(1-pentene) obtained with 1 was higher than that of the poly(1-pentene) synthesised with 2 . The degree of polymerisation was highly dependent on the metallocene catalyst. Oligomers ranging from the dimer of 1-pentene to poly(1-pentene) with a number-average molar mass M_n = 5100 g mol^–1 were formed. The ¹H NMR spectra of the samples were analysed with regard to functional groups and these were attributed to different chain termination processes. A MALDI-TOF spectrum of low-molar-mass poly(1-pentene) could be recorded using dithranol as matrix and adding silver trifluoroacetate to promote ion formation.     

Crystallization and morphology of the trigonal form in random propene/1-pentene copolymers

The melting and crystallization behaviour of a series of isotactic propene/1-pentene random copolymers, with 1-pentene contents up to 50 mol%, was investigated by DSC and temperature resolved WAXD/SAXS. The role of the 1-pentene comonomer in the development of the trigonal modification (δ-form) of i-PP was studied and the results were compared with those reported in the literature for PP copolymers with 1-hexene. The crystallizing capability of the δ-form, which develops in the composition range between ca. 10 and 50 mol% of 1-pentene content, only slightly decreases with concentration of 1-pentene. This result is correlated with the limits imposed to cell expansion by the crystal density. The crystallinity degree calculated from the deconvolution of the WAXD patterns is in fair agreement with the results of the DSC analysis, from which the value of the melting enthalpy of the perfect i-PP δ-form has been estimated to be around 140 J/g. The crystallization kinetics of the trigonal modification is characterized by a composition-dependent induction time followed by a relatively fast development of structural order. The sharp WAXD reflections combined with the SAXS data suggest that, notwithstanding the intrinsic intrachain structural disorder, thin and wide lamellae characterize the morphology of the δ-form crystallites.     

Copolymerization and characterization of ethene–1‐hexene copolymers prepared by using the (Me5Cp)2ZrCl2–MAO catalyst system

It is demonstrated that the catalyst system bis(pentamethylcyclopentadienyl)‐zirconium dichloride (Me₅Cp)₂ZrCl₂–methylaluminoxane (MAO) is able to produce random copolymers of ethene and 1‐hexene. The 1‐hexene incorporation in the copolymers is extremely small. Even in the case of a molar ratio of [ethene] to [1‐hexene] of 1/20 in the monomer feed, only 1.4 mol % 1‐hexene are incorporated according to ¹³C nuclear magnetic resonance (NMR) spectra. Nevertheless, the physical properties of the random copolymers change significantly in this small range of 1‐hexene incorporation, from a high‐density polyethene to a linear low‐density polyethene. Thus, the melting temperature, the degree of crystallinity, the density and lamella thickness, and the long period of the alternating crystalline and amorphous regions decrease with increasing 1‐hexene content in the random copolymers. Blends of high‐density polyethene prepared with the system (Me₅Cp)₂ZrCl₂–MAO and an elastomeric random copolymer of ethene and 1‐hexene are phase‐separated and show good compatibility, as demonstrated by transmission electron microscopy. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 439–447, 1999     

Polymerization of vinyl chloride with butyllithiums and metallocene catalysts

Polymerizations of vinyl chloride (VC) with butyllithium (BuLi) and metallocene catalysts were investigated. In the polymerization of VC with BuLi, the activity for polymerization decreased in the following order; t‐BuLi > n‐BuLi > s‐BuLi. A polymer controlled structurally in the main chain was found to be synthesized from the polymerization of VC with BuLi. The molecular weights of polymers obtained in bulk polymerization were higher than those of polymers obtained in solution. A linear relationship of the M_n of the polymer and the polymer yields was observed. The M_w/M_n of the polymer did not change significantly during polymerization, although the M_w/M_n was around 2. Thermal stability of the polymer obtained with BuLi was higher than that of polymer obtained with radical initiators, as determined by TGA measurements. In the polymerization of VC with Cp*TiX₃/MAO (X: Cl and OCH₃) catalysts, polymers were obtained with both catalysts, although the rate of polymerization was slow. The Cp*Ti(OCH₃)₃//MAO catalyst in CH₂Cl₂ gave higher‐molecular‐weight polymers in a better yield than in toluene. From elemental analysis and the NMR spectra of the polymers, the Cp*Ti(OCH₃)₃/MAO catalyst gave polymers consisting of repeating regular head‐to‐tail units, in contrast to the Cp*TiCl₃/MAO catalyst, which gave polymers having anomalous units.     

Crystallization analysis fractionation of ethene/1-hexene copolymers made with the MAO-activated dual-site (1,2,4-Me3Cp)2ZrCl2 and (Me5Cp)2ZrCl2 system

Different poly(ethene-co-1-hexene) samples with varying amounts of 1-hexene were characterized by crystallization analysis fractionation (Crystaf). The samples were synthesized with (1,2,4-Me₃Cp)₂ZrCl₂, (Me₅Cp)₂ZrCl₂, and a mixture of these two catalysts in a 1:1 molar ratio. In addition, preparative Crystaf was used to fractionate some of the samples made with the catalyst mixture into 1-hexene-rich and 1-hexene-poor fractions. These fractions were characterized by Crystaf, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC), and compared with copolymers made under similar conditions using the individual catalysts. Both (1,2,4-Me₃Cp)₂ZrCl₂ and (Me₅Cp)₂ZrCl₂ produced copolymers with unimodal distribution of short chain branches (SCBD), as expected for single-site catalysts. The catalyst mixture produced copolymers with bimodal SCBDs when 0.38 mol/l or higher concentrations of 1-hexene were used. The high temperature peak results from crystallization of polymer chains with few comonomer units, and these are attributed to (Me₅Cp)₂ZrCl₂. The low temperature peak results from crystallization of polymer chains made by (1,2,4-Me₃Cp)₂ZrCl₂, and these chains contain many comonomer units. Direct evidence for relative activity enhancement of the (Me₅Cp)₂ZrCl₂ catalyst in the dual-site system was observed.     

Ethylene/α‐olefin copolymerization by nonbridged (cyclopentadienyl)(aryloxy)titanium(IV) dichloride/AliBu3/Ph3CB(C6F5)4 catalyst systems

A series of nonbridged (cyclopentadienyl) (aryloxy)titanium(IV) complexes of the type, (η⁵‐Cp′)(OAr)TiCl₂ [OAr = O‐2,4,6‐^tBu₃C₆H₂ and Cp′ = Me₅C₅ ( 1 ), Me₄PhC₅ ( 2 ), and 1,2‐Ph₂‐4‐MeC₅H₂ ( 3 )], were prepared and used for the copolymerization of ethylene with α‐olefins (e.g., 1‐hexene, 1‐octene, and 1‐octadecene) in presence of AlⁱBu₃ and Ph₃CB(C₆F₅)₄ (TIBA/B). The effect of the catalyst structure, comonomer, and reaction conditions on the catalytic activity, comonomer incorporation, and molecular weight of the produced copolymers was examined. The substituents on the cyclopentadienyl group of the ligand in 1 – 3 play an important role in the catalytic activity and comonomer incorporation. The 1 /TIBA/B catalyst system exhibits the highest catalytic activity, while the 3 /TIBA/B catalyst system yields copolymers with the highest comonomer incorporation under the same conditions. The reactivity ratio product values are smaller than those by ordinary metallocene type, which indicates that the copolymerization of ethylene with 1‐hexene, 1‐octene, and 1‐octadecene by the 1–3/ TIBA/B catalyst systems does not proceed in a random manner. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A Strategy for Preparing Star Polymers Containing Metal–Metal Bonds Along the Polymeric Arms Using Click Chemistry

The [(η⁵-C₅H₄(CH₂)₃N₃)Mo(CO)₃]₂ dimer (3) was prepared and used to determine if the Huisgen cycloaddition reaction could be used to synthesize high molecular weight star polymers with metal–metal bonds in the arms. Several different click catalysts were examined. Cp*Ru(PPh₃)₂Cl (Cp* = η⁵-C₅(CH₃)₅) was previously shown to catalyze the formation of metal–metal bond-containing polymers using click chemistry; however, this catalyst underwent a Staudinger reaction with dimer 3 when a model coupling reaction was attempted with phenylacetylene. In order to avoid the Staudinger reaction, Cp*Ru(COD)Cl was used as the catalyst in the reaction of 3 with phenylacetylene, and coupling was observed after 14 h. Synthesis of a star polymer was attempted with 3 and 1,3,5-triethynylbenzene. Instead of coupling, Cp*Ru(COD)Cl reacted with the 1,3,5-triethynylbenzene. A third catalyst, Cu(IMes)Cl (IMes = 1,3-dimesityl-imidazol-2-ylidene) was used to couple 3 with 1,3,5-triethynylbenzene in 48 h. Both a high molecular weight polymer (M _n  = 77,000 g mol^?1) and a tripodal star core (M _n  = 1,800 g mol^?1) were successfully prepared with this catalyst.     

Carbon-13 NMR investigation of spin-lattice relaxation mechanism of poly(4-methyl-1-pentene)

Carbon-13 spin-lattice relaxation rates (1/T₁) and nuclear Overhauser enhancement (NOE) measurements were performed on poly(4-methyl-1-pentene) above the glass transition temperature in order to explain the segmental motion of the molecule by means of high resolution nuclear magnetic resonance spectroscopy. Experiments were carried out for poly(4-methyl-1-pentene) with low, medium, and high molecular weights. The similarity of the T₁ values showed that for polymers with a degree of polymerization (DP) > 100 the relaxation behavior of the carbon atoms no longer depends on molecular weight. The temperature effects were studied at 358, 363, 373, 383, 393, and 403 K, both on 25.18 and 100.61 MHz magnetic fields. Finally, several mathematical T₁ models were applied to study the change of T₁ encountered by the individual carbon atoms. The results reveal that the more factors being considered in the calculation the more consistent will be the results obtained with the T₁ model. A comparison showed that parameters used in the DLM T₁ model gives the best fit. © 1994 John Wiley & Sons, Inc.     

Carbon-13 nuclear magnetic resonance study of ethylene-1-octene and ethylene-4-methyl-1-pentene copolymers

Detailed assignments of ¹³C n.m.r. signals of ethylene-1-octene and ethylene-4-methyl-1-pentene copolymers, members of the linear low-density polyethylene (LLDPE) family, are presented. The equations relating signal intensities to the monomer sequences are given. Using these equations, the characterization of these copolymers by the triad monomer sequences is possible. From the analysis by the triad sequence, it is suggested that these 1-olefins have a tendency to be present isolated in the copolymer chain.     

Synthesis and Structure of New Dimeric Cyclopentadienyl Titanium Fluorine–Oxygen Systems: [Cp*TiF(μ-F)(μ-OPOPh2)]2, [Cp*TiF(μ-F)(μ-OSO2-p-C6H4Me)]2 and [Cp*TiF2(μ-OMe)]2

The reactions of Cp*TiF₃ with Me₃SiOPOPh₂, Me₃SiOSO₂-p-C₆H₄Me, and Al(OMe)₃ resulted in the formation of the dimers [Cp*TiF(μ-F)(μ-OPOPh₂)]₂ 1 , [Cp*TiF(μ-F)(μ-OSO₂-p-C₆H₄Me)]₂ 2 , and [Cp*TiF₂(μ-OMe)]₂ 3 , respectively, in good yields. In contrast to the formation of 3 , Cp*TiF₃ reacts with Al(OH)₃ to afford the known tetramer [Cp*TiF(μ-O)]₄ 4 . The structures of 1–3 have been determined by X-ray crystallography; compounds 1 and 3 crystallize in the monoclinic space group P2₁/c and compound 2 in the monoclinic space group P2/n. Compound 1 is the first example of a dimeric Cp*-titanium phosphinate containing a fluorine ligand. The core of the dimeric structure of both 1 and 2 consists of two Ti atoms bridged by two fluorine atoms and two bidentate groups. In contrast, the dimeric structure of 3 consists of two Ti atoms bridged only by two methoxy groups. An equilibrium of isomers of 1 and 2 has been observed in solution by ¹H and ¹⁹F NMR. The ¹⁹F NMR spectra of 1–3 are discussed in detail.     

Skeletal isomerization kinetics of 1-pentene over an HZSM-22 catalyst

Synthesis of the oxygenate fuel additive TAME (tertiary amyl methyl ether) is based on the reaction between reactive isopentene compounds (2-methyl-1-butene and 2-methyl-2-butene) and methanol. Skeletal isomerization of n-pentenes is an important reaction route in production of the raw material for TAME synthesis. In this work the kinetics of skeletal isomerization of 1-pentene was studied using HZSM-22 as a catalyst, and the effect of temperature (523–598 K) and WHSV (weight hourly space velocity) on product composition were investigated. The observed main reaction products were cis- and trans-2-pentenes, 2-methyl-2-butene, 2-methyl-1-butene and 3-methyl-1-butene. Minor products found in the output stream were C₂, C₃, C₄, C₆, C₇, C₈ and C₁₀ – alkenes and – alkanes. Only traces of methane and C₉ compounds were detected. Two different reaction mechanisms have been proposed in literature for skeletal isomerization of n-pentenes and their side reactions (dimerization and fragmentation); the monomolecular and the bimolecular skeletal isomerization mechanisms. In the current work a pseudohomogeneous reaction model for both mechanisms is fitted to experimental data. The fitting results show that both reaction mechanisms explain the skeletal isomerization of 1-pentene to isopentenes well. However, the monomolecular reaction mechanism explained the formation of dimerization and fragmentation products slightly better. The reliability of the estimated Arrhenius parameters was analyzed using Bayesian inference and Markov chain Monte Carlo methods (MCMC) which are rarely used in chemical engineering.     

Copolymerization of propene and 1-hexene with isospecific and syndiospecific metallocene catalysts

SUMMARY SUMMARY Copolymerization of propene and 1-hexene has been carried out in toluene at 30°C in the presence of homogeneous methylaluminoxane (MAO)-activated 3 ansa-metallocenes, highly syndiospecific iPr(Cp)(Flu)ZrMe₂ ( 1 ), lower syndiospecific Et(Cp)(Flu)ZrMe₂ ( 2 ), and isospecific rac-(EBTHI)ZrMe₂ ( 3 ), in order to study the role of catalyst stereospecificity on comonomer incorporation. The incorporation of 1-hexene decreases in the following order: highly syndiospecific 1 /MAO catalyst > lower syndiospecific 2 /MAO catalyst > isospecific 3 /MAO catalyst. All copolymer chains contain the comonomer in nearly random distribution. The copolymers produced by 1 /MAO and 3 /MAO catalysts were composed of uniform chains, but that by 2 /MAO was fractionated into many fractions in the solvent extraction. Considerable rate enhancements were recorded in the copolymerization when the feed ratio of 1-hexene to propene is around 0.6 for all catalysts. Received: 16 December 1997/Revised version: 9 February 1998/Accepted: 19 February 1998     

Preparation of Polymers Containing Metal–Metal Bonds along the Backbone Using Click Chemistry

The [(η⁵-C₅H₄(CH₂)₃OC(O)(CH₂)₂C≡CH)Mo(CO)₃]₂ complex (1) was synthesized and used to explore the feasibility of using the Huisgen cycloaddition reaction (a click reaction) to incorporate molecules with metal–metal bonds into polymer backbones. In a model reaction, coupling of 1 with benzyl azide was observed in 24 h using Cp*Ru(PPh₃)₂Cl as a catalyst. In contrast, the reaction of 1 with benzyl azide using a CuBr/ligand catalyst (where the ligand is either PMDETA or bipyridine), resulted in disproportionation of the Mo–Mo unit in 1. Complex 1 was also coupled with telechelic azide-terminated polystyrene oligomers. With either the CuBr/PMDETA or CuBr/bipyridine catalyst, disproportionation of the Mo–Mo bonded unit occurred before complete coupling was observed. The reaction was also slow when the Cp*Ru(PPh₃)₂Cl catalyst was used; however, no disproportionation products were observed and a high molecular weight polymer (M _n = 120,000 g/mol) was produced. The Cp*Ru(PPh₃)₂Cl catalyst was also used to couple 1 with azide-terminated poly(ethylene glycol). After 15 h, this reaction produced a polymer with M _n = 73,000 g mol⁻¹. It is concluded that, although somewhat slow, click chemistry using the Cp*Ru(PPh₃)₂Cl catalyst is an excellent method for synthesizing high molecular weight polymers with metal–metal bonds along the backbone.     

Copolymerization of Propylene with 1-Hexene and 4-Methyl-1-Pentene in Liquid Propylene Medium. Synthesis and Characterization of Random Metallocene Copolymers with Isotactic Propylene Sequences

Summary Propylene copolymerization with 1-hexene and 4-methyl-1-pentene in liquid propylene medium in presence of MAO-activated C₂-symmetry ansa-zirconocene rac-Me₂Si(4-Ph-2-MeInd)₂ZrCl₂ was studied. Random copolymers of propylene with 1-hexene and 4-methyl-1-pentene content up to 7 mol % were obtained at 60 °C. General kinetic characteristics of propylene/higher α-olefin copolymerization were evaluated. The distinct feature of propylene copolymerization with 1-hexene and 4-methyl-1-pentene in liquid propylene medium – the proximity of comonomer relative reactivity ratios (r₁∼r₂∼1) that indicates azeotropic nature of copolymerization processes in studied conditions. Synthesized copolymers were characterized with the use of IR, ¹³C NMR, GPC, WAXD, DSC techniques, and uniaxial tensile testing.     

Umsetzungen des Pentamethylcyclopentadienyl‐Halbsandwichkomplexes Cp*Ta(CO)4 mit Chlor,Brom und Iod

The reaction of Cp*Ta(CO)₄ ( 1 ) (Cp* = η⁵‐pentamethylcyclopentadienyl, η⁵‐C₅Me₅) with chlorine leads to Cp*TaCl₄ ( 2a ), whereas the corresponding reactions with bromine or iodine give the oxo‐bridged complexes [Cp*TaX₃]₂(μ‐O) (X = Br ( 3b ), I ( 3c )). The oxygen atom apparently stems from a carbonyl ligand. In the presence of air, the binuclear complexes 3a , b are converted into mononuclear Cp*Ta(O)X₂ ( 4b , c ). The X‐ray structural determination of [Cp*TaBr₃]₂(μ‐O) ( 3b ) confirms a linear Ta–O–Ta bridge with a Ta–O distance of 190,4(1) pm.     

1H NMR spectroscopic differentiation of block copolymer,random copolymer and mixture of the corresponding homopolymers through end group and monomer sequence analyses

Summary Highly isotactic block and random copolymers of methyl methacrylate (MMA) and ethyl methacrylate (EMA) were prepared witht-C₄H₉MgBr in toluene at-60°C.¹H NMR spectra of the copolymers were measured in nitrobenzene-d₅ at 110°C and 500 MHz and analyzed in regard to monomer sequence and the end group. NMR signals due to the monomeric units provide clear indications for distinguishing the block copolymers from the random copolymers. The chemical shift of the initiator fragment signal is so sensitive to the adjacent monomeric unit that PMMA-block-poly(EMA) and poly(EMA)-block-PMMA can be differentiated spectroscopically. The main part of the spectrum for a mixture of PMMA and poly(EMA) prepared witht-C₄H₉MgBr is identical to those for the block copolymers but the mixture shows twot-C₄H₉-signals arising from both homopolymers and thus can be distinguished from the block copolymers.     

Synthesis of maleic and pHthalic anhydrides from the mixture of cyclopentene and 1-pentene

The selective oxidations of cyclopentene, 1-pentene, and their mixture to maleic and phthalic anhydrides have been studied to gain information on the total utilization of olefins of C₅-fraction. The highest selectivities for maleic anhydride, a single major organic product, in individual oxidations of cyclopentene and 1-pentene were obtained at complete or almost complete conversion, and then the main byproduct was phthalic anhydride. The cooxidation of the mixture of cyclopentene and 1-pentene at ca. 100% conversion, which was selected as optimized condition, gave no interaction between cyclopentene and 1-pentene. This result indicates that two reactants can be simultaneously utilized at one oxidation unit process. In contrast, the cooxidation at low degrees of conversion gave some interaction. It was only related to the slightly stronger adsorption of cyclopentene as compared to 1-pentene.     

Support and precursor effects on the preparation of new heterogenized Pt/Sn catalysts for the selective hydroformylation of 1-pentene

New heterogenized Pt/Sn catalysts selective for the hydroformylation of 1-pentene have been synthesized. The complex cis-[PtCl₂(PPh₃)₂] and the SnCl₂.2H₂O or SnC₂O₄ precursors have been anchored on silica-, magnesia- and alumina-carriers. X-ray photoelectron spectroscopy was used to determine the surface composition and the nature of the anchored species. The hydroformylation activity was found to depend on the type of support and tin precursor used. Only the silica supported catalysts were active in the hydroformylation reaction. Samples prepared from SnCl₂-2H₂O were 200-fold more active than those prepared from SnC₂O₄. Selectivity ton-hexanal of the silica-supported catalyst prepared from SnCl₂-2H₂O was as high as 94.4% at 39.2% conversion of 1-pentene.