Catalyst Systems For Polymerization Research Articles

Water-tolerant catalyst systems for the bulk cationic polymerization of para-methylstyrene and indene

Water-tolerant catalyst systems have been investigated for the cationic oligomerization of technical-grade p-methylstyrene and indene, for the production of industrially relevant aromatic resins. Systems based on 1- p-tolylethanol and 1-indanol (ROH) as initiators, in association with Cu(OTf) 2, Bi(OTf) 3 (OTf = triflate) and B(C 6F 5) 3 as co-initiators/catalysts, show interesting productivities at 60 °C under air, with as low as 0.2–1.0 mol% catalyst loading. Most of the reactions are not controlled in terms of molecular weights of the products, except for indene oligomerization by the borane catalyst where experimental M n values match well the theoretical values, as determined by the amount of added initiator over a 5-fold range (with 2–10 mol% vs. monomer). The ROH/tris(pentafluorophenyl)borane system offers the best compromise in terms of productivity and control over the molecular weights of the oligomers, which can be manipulated by the amount of initiator and reaction temperature.

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 Mw 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

Studies of the aging effect on the level of isocyanate residues in polyester-based can coating systems

A methyl ethyl ketone oxime-blocked isocyanate was used as a crosslinking agent in the curing of polyester–polyurethane (PEPU) can coatings. The completeness of cure was assessed from the amount of residual (un-reacted) isophorone diisocyanate (IPDI) trimer that was presented in the coating after curing. This amount of residual trimer depended strongly on the temperature at which the curing was undertaken and time given for curing. The degree of cure was also assessed, correlating with the reduced IPDI trimer migration potential. The amount of residual IPDI trimer that was extractable from a typical PEPU coating rose markedly (15- to 20-fold) if the wet coating was aged up to 6 months before use. The presence of a TiO2 pigment increased the aging effect. An aluminum flake pigment had an even greater effect. The TiO2 pigment increased aging by different degrees according to the type of surface modification that had been applied to the pigment. The grade having the greatest alumina content, as a result of surface modification, gave the greatest aging. The undesirable effects of aging were counteracted by the addition of more catalyst to the aged coating just before the coating was used to coat panels. Deactivation of the acidic polymerization catalyst system (based on organotin compounds) is thought to be the cause of this aging. These findings have allowed improvements to be made to the specifications of the pigments and the catalysts used, with respect to the consistent industrial production of low migration coatings.

Complexes of Mg, Ca and Zn as homogeneous catalysts for lactide polymerization

Interest in the utility of polylactide as a commodity polymer has increased significantly in recent years due to numerous environmental advantages over conventional petrochemically derived plastics. As such, the development of novel catalyst systems for the ring opening polymerization of lactide has seen tremendous progress in the past decade. In particular, divalent metals (i.e. Mg, Ca and Zn) supported by monoanionic ancillary scaffolds are appealing because of their low toxicity and cost. A much less common approach involves the use of neutral ligands in combination with the aforementioned divalent metal centres. The additional valence thus renders it possible, upon reaction with traditional Lewis or Brønsted acid activators, to generate sterically and electronically unsaturated species, akin to the most widely employed olefin polymerization catalysts. This Perspective is not intended as a comprehensive review, but rather a systematic highlight of key contributions, which have served to extend the forefront of this exciting field.

An investigation of the influence of R on the abilities of the polar monomers CH2CH(CH2)8OR (R = Me, PhCH2, Ph3C, Me3Si, Ph3Si) to participate in O- rather than η2-coordination to metallocene alkene polymerization catalysts; an unanticipated role for ether oxygen coordination in promoting polymerization

Copolymerization of ethylene and propylene with polar monomers of the types CH(2)=CH(CH(2))(n)OH (n = 1-12) in order to introduce polar functionality into the resulting polymers is possible in principle if the hydroxyl groups of the polar monomers are masked such that they cannot coordinate to Lewis acidic catalyst sites and prevent eta(2)-alkene coordination. Although the use of hydrolysable ethers of the types CH(2)=CH(CH(2))(n)OR (R = alkyl, silyl; n = 1-12) is a protecting group strategy, which has been investigated somewhat, in fact this approach has not been investigated systematically and little is known of the effectiveness of various R groups in hindering oxygen coordination to e.g. metallocene polymerization catalyst systems. We report here the results (a) of an NMR study of reactions of an archetypal metallocene polymerization catalyst, Cp(2)ZrMe(mu-Me)B(C(6)F(5))(3), with the polar monomers CH(2)=CH(CH(2))(8)OR (R = Me, PhCH(2), Ph(3)C, Me(3)Si, Ph(3)Si), all protected versions of the readily available, long chain polar monomer 9-decen-1-ol, and (b) of an investigation of the copolymerization reactions of these same polar monomers with ethylene and propylene catalyzed by the well known rac-C(2)H(4)(Ind)(2)ZrCl(2)/MAO catalyst system. While increasing the steric requirements of the groups R does decrease the apparent abilities of the ethers to displace [BMe(C(6)F(5))(3)](-) from the [Cp(2)ZrMe](+) cation, there is no correlation of size of R with the degrees of incorporation of the polar monomers into copolymers of ethylene and propylene. Instead, a heretofore unsuspected role for catalyst activation by the ether linkage is suggested.

Comparison of Syndiotactic Polystyrene Morphology Obtained Via Heterogeneous and Homogeneous Polymerization with Metallocene Catalyst

AbstractSummary: Supported catalyst system for the slurry phase polymerization of styrene in toluene was prepared by the immobilization of 2‐methylindenyltrichlorotitanium(2‐MeIndTiCl3) on silica and activation of this catalyst was performed by methylaluminoxane(MAO) in polymerization media. Homogeneous polymerization of styrene with 2‐methylindenyltrichlorotitanium activated by MAO was performed in toluene. The morphology of obtained syndiotactic polystyrene (sPS) via heterogeneous and homhgeneous catalyst system was compared. Polymerization of styrene by homogeneous catalyst lead to formation of gel and resultant polymers presented a compact and dense texture while the global gelation do not occur with silica supported catalyst at different Ti/SiO2 mol ratios and sPS was obtained as separated particles. Unlike to the homogeneous catalyst, obtained polymers showed a porous texture. Highly porous texture of sPS was obtained with Ti/SiO2 = 0.5% mol ratio.

Olefin polymerisation catalysts

This chapter investigates methylalumoxane (MAO)-free new olefin polymerization catalyst systems based on FI Catalysts. The chapter investigates MgCl2 as a cocatalyst for the bis(phenoxy-imine) complexes to develop high performance catalysts based on the complexes. Ethylene polymerizations were performed using the resulting mixture of the dealcoholysis product as an activator. The resulting aluminum species of the dealcoholysis product probably work as in situ alkylating reagents for complexes as well as scavengers in a polymerization system. To confirm the chemically homogeneous catalysis of the systems, copolymerization of ethylene with propylene was performed and the comonomer composition distribution of the resulting copolymer was investigated. Gel permeation chromatography–infrared (GPC–IR) analysis revealed that the copolymer possesses narrow propylene composition distribution, showing that the system is single-site catalyst. GPC analyses indicate that the polyethylenes (PEs) formed with catalyst systems possess narrow molecular weight distributions of 2.66 and 2.67, suggesting that the polymers are produced by single active species.

Polymerization of norbornene with a pendent sulfonyl fluoride group catalyzed by palladium complex bearingtBu3P ligand

The combination of palladium complex (tBu3P)Pd(Me)Cl (1) and NaB[3,5-(CF3)2C6H3]4 (NaBAr4) catalyzed homopolymerization of a novel monomer, norbornene (NB) with a pendent 2-fluorosulfonyltetrafluoroethoxymethyl chain (NBSF). Catalytic activities of 1/NaBAr4 were higher than those of previously reported palladium or nickel catalysts, probably, because the palladium center with electron donative tBu3P ligand was barely poisoned by the sulfonyl fluoride coordination. Thus, 1/NaBAr4 is the current best catalyst system for NBSF polymerization. The catalyst system also gave copolymers of NB with NBSF. The obtained copolymers have high sulfonyl-fluoride incorporation and a narrow molecular weight distribution. Present catalyst system could control incorporation ratio of NBSF by changing a feed monomer ratio with slow addition of NB solution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5133–5141, 2008

Kinetic and Active Centre Studies on the Polymerization of Propylene using MgCl2 Supported Ziegler – Natta Catalysts and 1,3 Diether Donors

AbstractAll polymerization experiments were carried out in a Büchi glass reactor capable of operating at propylene pressures of 1‐7 atmospheres. Two types of MgCl2 supported catalysts with controlled morphology were studied, viz., catalyst systems containing either a 1,3 diether (Catalysts A and D), 9,9‐bis (methoxymethyl) fluorene, or a simple diester (Catalysts B, C and E) such as diisobutylphthalate, used as reference systems. The kinetic behaviours of these catalysts were investigated for propylene polymerization. The 1,3‐diether based systems proved to be excellent catalyst systems for propylene polymerization showing high polymerization activities and stable rate‐time profiles and produced spherical polymer particles. Catalyst pre‐treatment was found to play an important role in controlling the morphology of the final polymer. A tritiated alcohol radio‐quenching technique was used to determine the concentrations active centres: values of 7.5 and 5.1 mol/mol % respectively were obtained for catalysts A and D and 3.5, 2.9 and 2.2 mol/mol % respectively were obtained for catalysts B, C and E. Catalysts A and D showed very high polymerization activities and also higher C0* values. All polymers produced were characterized by SEM, DSC, extraction and molecular weight determinations.

Semibatch Atom Transfer Radical Copolymerization of Styrene and Butyl Acrylate

AbstractSummary: Batch and semibatch butyl acrylate (BA) polymerizations are carried out using a heterogeneous atom transfer radical polymerization (ATRP) catalyst system, with excellent molecular weight (MW) control maintained at temperatures below 80 °C. A kinetic model, using rate coefficients from literature and catalyst solubility data from this study, provides a good representation of the experimental results, after modifying the model to account for the decrease in rate caused by intramolecular chain transfer. It is also demonstrated experimentally that well‐defined random, gradient, and block styrene/BA copolymers can be synthesized by manipulating monomer feed profiles in the ATRP semibatch process.

Use of Drug Discovery Tools in Rational Organometallic Catalyst Design

A computational procedure is detailed where techniques common in the drug discovery process-2D- and 3D-quantitative structure-activity relationships (QSAR)-are applied to rationalize the catalytic activity of a synthetically flexible, Ti-N=P ethylene polymerization catalyst system. Once models relating molecular properties to catalyst activity are built with the two QSAR approaches, two database mining approaches are used to select a small number of ligands from a larger database that are likely to produce catalysts with high activity when grafted onto the Ti-N=P framework. The software employed throughout this work is freely available, is easy to use, and was applied in a "black box" approach to highlight areas where the drug discovery tools, designed to address organic molecules, have difficulty in addressing issues arising from the presence of a metal atom. In general, 3D-QSAR offers an efficient way to screen new potential ligands and separate those likely to lead to poor catalysts from those that are likely to contribute to highly active catalysts. The results for 2D-QSAR appear to be quantitatively unreliable, likely due to the presence of a metal atom; nonetheless, there is evidence that qualitative predictions from different models may be reliable. Pitfalls in the database mining techniques are identified, none of which are insurmountable. The lessons learned about the potential uses and drawbacks of the techniques described herein are readily applicable to other catalyst frameworks, thereby enabling a rational approach to catalyst improvement and design.

Efficient preparation of isotactic polypropylene/montmorillonite nanocomposites by in situ polymerization technique via a combined use of functional surfactant and metallocene catalysis

In order to promote efficiency of the preparation of isotactic polypropylene (i-PP)/montmorillonite (MMT) nanocomposites by in situ polymerization technique, a strategy was laid out to enhance both the intercalative selectivity and the catalyst activity of the in situ polymerization by a combined use of a functional surfactant for MMT modification and a metallocene catalyst system for isospecific propylene polymerization. Thus, (2-hydroxylethyl) hexadecyl diethylammonium iodine was involved in the ion-exchanged organic modification of MMT, leading to an implantation of catalyst-anchoring reactive sites (hydroxyl, OH) in the interlayer galleries of MMT (OMMT). By treating the OH-intercalated OMMT successively with excessive methylaluminoxane (MAO) and rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2, the metallocene catalyst typical for i-PP polymerization was stabilized inside the interlayer galleries with a catalytically benign environment. The MMT-borne catalyst, upon further activation by MAO, released fairly high activities for propylene polymerization. The effective intercalative polymerization ensured an efficient preparation of i-PP/MMT nanocomposite. A series of i-PP/MMT nanocomposites containing completely disordered MMT at a loading range of 1.0–6.7wt% (TGA measurement residue at 600°C) were obtained in high yields.

Synthesis of Novel Polymers with a Chiral 1,2‐Diamine Moiety by Polycondensation and their Application to Catalyst for Asymmetric Hydrogenation of Aromatic Ketones

AbstractSummary: Novel polymers with chiral 1,2‐diamine moiety were successfully synthesized by polycondensation of N‐Boc protected enantiopure 1,2‐diamine bearing two phenol groups (S,S)‐4, bisphenol derivatives, and dibromides, followed by deprotection of N‐Boc moiety. Hydrogenation of acetophenone was performed with use of polymeric catalyst system prepared from the polymer‐supported chiral 1,2‐diamine and RuCl2/(S)‐BINAP. The reaction proceeded smoothly even in 2‐propanol to give 1‐phenylethanol in quantitative yield with high level of enantioselectivity. Furthermore, various other aromatic ketones could be asymmetrically hydrogenated by the polymeric catalyst system.

Polymer‐Supported Chiral 1,2‐Diamines by Radical Copolymerization with Vinyl Monomer for Asymmetric Hydrogenation of Aromatic Ketones

AbstractNovel polymer‐supported chiral 1,2‐diamines have successfully synthesized by radical copolymerization of N‐Boc protected enantiopure 1,2‐diamine bearing two vinylphenyl moieties ((S,S)‐5) with various achiral vinyl monomer including methyl methacrylate, 2‐hydroxyethyl methacrylate, butyl acrylate, and N‐isopropyl acrylamide, followed by deprotection of N‐Boc moiety. Hydrogenation of acetophenone in 2‐propanol/DMF mixed solvent was performed with use of polymeric catalyst system prepared from the polymer‐supported chiral 1,2‐diamine and RuCl2/(S)‐BINAP. The reaction proceeded smoothly to give 1‐phenylethanol in quantitative yield with high level of enantioselectivity. In addition, various other aromatic ketones could be asymmetrically hydrogenated by the polymeric catalyst system. Furthermore, the polymeric catalyst could be reused several times in hydrogenation of aromatic ketones without loss of the enantioselectivity.

Fundamentals and development of high‐efficiency supported catalyst systems for atom transfer radical polymerization

AbstractAtom transfer radical polymerization (ATRP) is a controlled/living radical polymerization process developed a decade ago that allows the synthesis of tailored macromolecules. It has been widely used in the laboratory for polymer synthesis since but little use has been made of it at the industrial scale for polymer production. This is due to the low activity of the ATRP catalyst that is central to the process. Much work has been done over the years to overcome this challenge, and the greatest successes have been achieved through catalyst supporting and recycling. We present here a historical account of the development of supported ATRP catalysts while shedding light on their present and future challenges. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 553–565, 2007

Effects of molecular characteristics and processing conditions on melt‐drawing behavior of ultrahigh molecular weight polyethylene

AbstractThe effects of molecular characteristics and processing conditions on melt‐drawing behavior of ultrahigh molecular weight polyethylene (UHMW‐PE) are discussed, based on a combination of in situ X‐ray measurement and stress–strain behavior. The sample films of metallocene‐ and Ziegler‐catalyzed UHMW‐PEs with a similar viscosity average MW of ∼107 were prepared by compression molding at 180 °C. Stress profiles recorded at 160 °C above the melting temperature of 135 °C exhibited a plateau stress region for both films. The relative change in the intensities of the amorphous scattering recorded on the equator and on the meridian indicated the orientation of amorphous chains along the draw axis with increasing strain. However, there was a substantial difference in the subsequent crystallization into the hexagonal phase, reflecting the molecular characteristics, that is, MW distribution of each sample film. Rapid crystallization into the hexagonal phase occurred at the beginning point of the plateau stress region in melt‐drawing for metallocene‐catalyzed UHMW‐PE film. In contrast, gradual crystallization into the hexagonal phase occurred at the middle point of the plateau stress region for the Ziegler‐catalyzed film, suggesting an ease of chain slippage during drawing. These results demonstrate that the difference in the MW distribution due to the polymerization catalyst system dominates the phase development mechanism during melt‐drawing. The effect of the processing conditions, that is, the including strain rate and drawing temperature, on the melt‐drawing behavior is also discussed. The obtained results indicate that the traditional temperature–strain rate relationship is effective for transient crystallization in to the hexagonal phase during melt‐drawing, as well as for typically oriented crystallization during ultradrawing in the solid state. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2455–2467, 2006

Group 4 Metal Complexes of Nitrogen-Bridged Dialkoxide Ligands: Synthesis, Structure, and Polymerization Activity Studies

Neutral soluble titanium(IV) and zirconium(IV) complexes of new amino-dialkoxide ligands {OCR2CH2N(CH2Ph)CH2CR2O}2- ({ONOR}2-) have been prepared. Alcohol and alkane elimination reactions from {ONOR}H2 (R = Me, 1; p-tol, 2) and salt metathesis routes from Li2{ONOMe} in situ-generated afford {ONOMe}Ti(OiPr)2 (3), {ONOR}2M (R = Me, M = Ti, 5; Zr, 6; R = p-tol, M = Zr, 7), {ONOMe}Zr(CH2Ph)2 (8), {ONOMe}ZrCl2(THF)n (n = 0, 9; n = 1, 10), {ONOMe}Zr(NMe2)2 (11), and {ONOR}TiCl2 (R = Me, 13; R = p-tol, 14) in good yields. X-ray crystallographic studies showed that 3, 8, 13, and 14 adopt in the solid state mononuclear structures, with coordination of the nitrogen atom to the metal center. Dinuclear structures with bridging alkoxide and amido ligands were observed for 6 and a mixed amido-{ONOMe}Zr complex (12) isolated in the preparation of 11. NMR data are consistent with the existence of a single monomeric species in toluene solution for all complexes, except 11 and dichlorozirconium complexes 9 and 10, for which mixtures of monomeric and possibly aggregated species are observed in toluene and THF. The dynamic behavior of monomeric species 3, 8, 13, and 14 in toluene was investigated by variable-temperature NMR spectroscopy. The activation parameters determined by line-shape analysis, in particular for 8 (ΔH⧧ = 20.0 ± 1 kcal·mol-1; ΔS⧧ = 13.1 ± 2 cal·mol-1·K-1) and 13 (ΔH⧧ = 17.4 ± 1 kcal·mol-1; ΔS⧧ = 11.4 ± 2 cal·mol-1·K-1), suggest a process involving dissociation of nitrogen, inversion of configuration at nitrogen, and amine re-coordination. The bulkiness of the R substituents affects the fluxional behavior of {ONOR}TiCl2 (R = Me, 13; R = p-tol, 14). The THF-free dichlorozirconium complex 9 in combination with MAO generates highly active but very unstable ethylene polymerization catalyst systems.

Discovery and Optimization of New Chromium Catalysts for Ethylene Oligomerization and Polymerization Aided by High-Throughput Screening

High throughput screening (HTS) of a 205 member Schiff base salicylaldimine ligand library derived from salicylaldehydes bearing bulky ortho-substituents, i.e., 9-anthracenyl, 1,4,5,8-tetramethylanthracenyl or triptycenyl, reacted in-situ with (p-tolyl)CrCl2(thf)3, identified two new classes of highly active chromium based systems for the oligomerization and polymerization of ethylene, respectively. The polymerization system comprises bidentate ortho-substituted anthracenyl Schiff bases bearing small primary or secondary alkyl imine substituents. The oligomerization catalysts are based upon tridentate ortho-triptycenyl-substituted Schiff bases with pyridylmethyl or quinolyl substituents. Validation tests confirmed polymerization productivities of up to 3000 g x mmol(-1)h(-1)bar(-1) for the polymerization catalyst systems while the oligomerization catalysts gave productivities up to 10 000 g x mmol(-1)h(-1)bar(-1). Key catalyst precursors have been characterized by X-ray crystallography.

Unprecedented Syndioselectivity and Syndiotactic Polyolefin Melting Temperature: Polypropylene and Poly(4-methyl-1-pentene) from a Highly Active, Sterically Expanded η-Fluorenyl−η1-Amido Zirconium Complex

The structurally unique, sterically expanded eta1-fluorenyl-eta1-amido single-site precatalyst, Me2Si(eta1-N-tBu)(eta1-C29H36)ZrCl2.OEt2 (3), upon activation with methylaluminoxane (MAO), is remarkably active and constitutes the most syndioselective alpha-olefin polymerization catalyst system yet reported. 3/MAO affords as-prepared syndiotactic polypropylene with [rrrr] > 99% and unprecedented melting temperatures for the unannealed (165 degrees C) and annealed (174 degrees C) polymers. The activity of this system is 4 times that of the prototypical syndioselective catalyst Me2C(eta5-C5H4)(eta5-C13H8)ZrCl2/MAO. The high activity and syndioselectivity of 3/MAO can be extended to the production of syndiotactic poly(4-methyl-1-pentene) with a record melting temperature of 215 degrees C and [rrrr] = 97%.

Determination of the Kinetic Parameters of Atom Transfer Radical Polymerizations

In an attempt to find a novel catalyst system for atom transfer radical polymerization (ATRP), a parameter estimation method based on nonlinear regression was developed to evaluate various catalyst systems by determining kinetic parameters of polymerization. From our model system considering small molecular atom transfer addition reaction, we found that equilibrium constant of atom transfer reaction could be successfully determined using our parameter estimation method. However, the each value of activation rate constant and deactivation reaction constant is hard to be determined ubiquitously because of the poor sensitivities of them and the local minima trapping. By applying second minimization algorithm, the parameter estimation algorithm achieves higher propensity to reach global minimum, yet not all the time. The simulation results using kinetic rate constants determined by our method shows better agreement with the experimental data than that using literature values. This is because the current method uses fewer assumptions than other literature methods in determining rate constants. We also demonstrated the determination of kinetic constants in the polymerization of styrene and MMA using various metal catalysts, and the simulations using these kinetic constants agree well with the experimental data.