Catalyst Systems For Polymerization Research Articles

Horseradish peroxidase-catalyzed polyacrylamide gels: monitoring their polymerization with BSA-stabilized gold nanoclusters and their functional validation in electrophoresis.

Polyacrylamide gel (PAG) is extensively used as a matrix for biomolecular analysis and fractionation. However, the traditional polymerization catalyst system N,N,N',N'-tetramethylethylenediamine (TEMED)/ammonium persulphate (APS) of PAG presents non-negligible toxicity. Herein, we utilized the green and efficient bio-enzyme horseradish peroxidase (HRP) to catalyze the gel polymerization of polyacrylamide. At the same time, the efficacy of this gel system in separating nucleic acids and proteins was confirmed by applying the gel system in electrophoresis. This study aims to explore a higher biosafety polyacrylamide gel polymerization catalytic system which can be applied to electrophoresis technology. Furthermore, in order to differentiate between the bio-enzymatic catalytic system and the traditional toxic catalytic system during polymerization, aggregation-induced luminescence (AIE) of bovine serum albumin-stabilized gold nanoclusters (BSA-Au NCs) was used to monitor the polymerization reaction of the system. The results indicated that the fluorescence intensity of the polymeric system containing BSA-Au NCs increased with the polymerization of the monomers. Subsequently, we assessed whether certain components of nucleic acid electrophoresis and protein electrophoresis such as sodiumdodecylsulfate (SDS) and TBE buffer (Tris-boric acid, EDTA, pH 8.3) would affect the polymerization of the polyacrylamide gels catalyzed by the biological enzymes. The experimental conditions were also optimized to explore the optimal concentration of the ternary system of HRP, H2O2 and ACAC. Our results suggested that the bioenzyme-catalyzed system could be a feasible alternative to the TEMED/APS-catalyzed system, which also could provide new insights into the methods of monitoring the polymerization system.

The Nature and Role of the Nickel Species in the Ni(II) α-Diimine-based Ethylene Polymerization Catalyst Systems (A Review)

The Nature and Role of the Nickel Species in the Ni(II) α-Diimine-based Ethylene Polymerization Catalyst Systems (A Review)

Synthesis and characterization of cyclomatrix polyphosphazenes framework nanospheres-supported Cu0 nanocatalyst and its use in hydrogen production from ethylenediamine bisborane

In this study, Cp-BAP3@Cu catalyst system containing Cu0 nanoparticles with an average size of 4.23 ± 1.97 nm was prepared by using Cp-BAP nanospheres containing cyclotriphosphazene with an average size of 306.31 ± 61.54 nm as support material. Characterizations of the synthesized polymeric materials and catalyst system were carried out by various analysis techniques. The Cp-BAP3@Cu catalyst system was used for the catalytic hydrolysis reaction of ethylenediamine bisborane (EDAB). For the hydrolysis reaction of EDAB, Cp-BAP3@Cu had a turnover frequency of 1539 mol H2/mol Cu0. h at 30 °C. The activation parameters for the hydrolysis reaction were Ea = 47.36 ± 0.52 kJ/mol, ΔH0 = 44.73 ± 0.52 kJ/mol and ΔS0 = −153.81 ± 6.14 J/mol.K. The Cp-BAP3@Cu catalyst system has an important catalytic activity in the formation of H2 from the hydrolysis of EDAB.

Effect of type of polymerization catalyst system on the degradation and stabilization of polyethylenes in the melt state—Part 4: Comparative antioxidant effectiveness on organoleptic extractables

AbstractSeveral polyethylene resins using Ziegler, metallocene, and Phillips catalyst technologies were examined to obtain more detailed information about the effect of different polymerization catalyst systems on the production of extractable thermo‐oxidative degradation products formed during melt processing cycles. This produces volatile organoleptic components (VOCs and extractable) such as hydrocarbons, alcohols, aldehydes, ketones, and carboxylic acids. Although some of the oxidation products are in‐chain bound, many are produced as free, easily extractable entities or volatile components. The purpose of this study is to identify the nature of the products by gas chromatography–mass spectrometry (GC–MS) and FTIR analysis. The identity of the VOCs formed is necessary to modify the product's quality or establish which are toxic and/or leachable with food products. The results show that the evolution of carbonyl products, nature, and quantity is influenced significantly by the polymer type and catalyst used. Over 300 organoleptics low molar mass degradation products, such as alkane, alkene, carbonyl, and alcohol functionalities were detected by GC–MS analysis coupled with FTIR analysis on hexane extractables. Certain stabilizers can control the generation of certain functionalities and inhibit others. Of importance was the discovery of the relationship between additive activity and structure and inhibition of the formation of specific types of oxidation functionalities to a particular catalyst system.

New Ni(II)-Ni(II) Dinuclear Complex, a Resting State of the (α-diimine)NiBr2/AlMe3 Catalyst System for Ethylene Polymerization

A novel room-temperature stable diamagnetic nickel complex 2 was detected upon activation of Brookhart-type ethylene polymerization pre-catalyst LNiBr2 (1, L = 1,4-bis-2,4,6-trimethylphenyl-2,3-dimethyl-1,4-diazabuta-1,3-diene) with AlMe3. Using in situ 1H, 2H, and 13C NMR spectroscopy, as well as DFT calculations, this species has been identified as an antiferromagnetically coupled homodinuclear complex [LNiII(μ-Me)(μ-CH2)NiIIL]+Br−. Its behavior in the reaction solution is characteristic of the resting state of nickel catalyzed ethylene polymerization.

Recent developments in catalyst systems for selective oligomerization and polymerization of higher α-olefins

A comprehensive review of the recent developments on the use of various homogeneous and heterogeneous catalysts for the dimerization, oligomerization and polymerization of higher alpha olefins.

Polymeric aluminum porphyrin: Controllable synthesis of ultra-low molecular weight CO2-based polyols

Carbon dioxide-based polyols with ultra-low molecular weight (ULMW, Mn < 1000 g/mol) are emergent polyurethane precursors with economic and environmental benefits. However, the lack of effective proton-tolerant catalytic systems limits the development of this field. In this work, the polymeric aluminum porphyrin catalyst (PAPC) system was applied to the copolymerization of CO2 and propylene oxide, where sebacic acid, bisphenol A, poly(ethylene glycol), and water were used as chain transfer agents to achieve the controlled synthesis of CO2-polyols. The molecular weight of the resulting CO2-polyols could be facilely regulated in the range of 400–930 g/mol at low catalyst loadings, fully demonstrating its catalytic advantages of high activity, high product selectivity, and excellent proton tolerance of PAPC. Meanwhile, the catalytic efficiency of PAPC could reach up to 2.1–5.2 kg/g under organic CTA conditions, even reaching 1.9 kg/g using water as the CTA. The cPC content could be controlled within 1.0 wt% under the optimized conditions, indicating the excellent controllability of the PAPC system. ULMW CO2-polyols combines the advantages of low viscosity (∼3000 mPa s at 25 °C), low glass transition temperature (∼−73 °C), and high carbonate unit content (∼40%), which is important for the development of high-performance polyurethanes.

Dual roles of trifluoroborate in nickel-catalyzed ethylene polymerization: Electronic perturbation and anchoring for heterogenization

Brookhart-type α-diimine nickel and palladium catalysts have been extensively studied over the past several decades; however, the heterogenization of these metal complexes has received much less attention. In this contribution, we installed a trifluoroborate potassium substituent on an α-diimine framework. The ionic nature of trifluoroborate potassium endowed the α-diimine nickel complex with a strong affinity for the SiO2 support, while its electron-donating nature enhanced the catalyst stability and polyethylene molecular weight. In the presence of only 100 equiv. of Et2AlCl cocatalyst, the SiO2-supported catalyst demonstrated significantly better performance than its homogeneous analog during ethylene polymerization, with extremely high activity (1.42–6.53 × 107 g mol−1 h−1) and high thermal stability. The heterogeneous system led to the formation of high-molecular-weight polyethylenes (Mn 142,500–732,800 g/mol), narrow polydispersities (2.18–3.00), tunable branching densities (21–64 per 1000 carbon atoms), and great mechanical properties. Moreover, the efficient copolymerization of ethylene with comonomers such as methyl 10-undecenoate, 6-chloro-1-hexene or 5-hexenylacetate was achieved. These superior properties enabled by the trifluoroborate potassium moiety may inspire its applications in other polymerization catalyst systems.

Synthesis, Structural Studies, and Application of Aluminum Aryloxides for Ring-Opening Metathesis Polymerization

A series of aluminum aryloxides of types [Al(OAr)3] and [Al(OAr)2Cl] (Ar = 4-CH3C6H4, 4-PhC6H4, 2-iPr-C6H4, 2-tBu-C6H4, 2,6-iPr2C6H3, and 2,6-Cl2C6H3) were synthesized from commercially available reagents and structurally characterized by single X-ray diffraction studies. The structural evaluations for aluminum aryloxides revealed the formation of dinuclear clusters in the solid state. The solution behavior of the synthesized compounds was studied by multinuclear nuclear magnetic resonance (NMR) spectroscopy. The synthesized compounds were applied for the in situ generation of Ziegler–Natta catalyst systems for the ring-opening metathesis polymerization (ROMP) of nonconstrained olefins. The ligand exchange between WCl6 and Al-aryloxides followed by activation with aluminum alkyls resulted in the formation of ill-defined species showing enhanced ROMP reactivity compared to the related systems generated upon the ligand exchange between WCl6 and ArOH or isolated [W(OAr)4Cl2]. The benefits of using newly developed systems for the ROMP of cyclic olefins are their low costs and high molecular weights for polymerization products (Mw > 250 kDa). Moreover, an E/Z stereoselective control over the double C═C bond in the polymeric product was achieved upon tuning the steric volume at the aryloxide ligand framework.

Surface effect of the MgCl2 support in Ziegler–Natta catalyst for ethylene polymerization: A computational study

Ziegler–Natta (Z–N) catalyst is a remarkable catalyst for olefin polymerization in the petrochemical industry. However, the role of each component remains unclear because of the complicated constituents and structures. MgCl2 is a suitable support for Z–N catalyst, which can improve the activity and stereoselectivity during olefin polymerization and achieve large-scale production of polyolefin under mild conditions. In exploring the role of MgCl2 in the Z–N catalyst system for ethylene polymerization, the stable surface of undercoordinated Mg cations, including (104), (101), (012), (110), and (015) in α-MgCl2 and (010), (011), (012), (110), and (111) in β-MgCl2 was used to load the catalyst, and the mechanism of ethylene polymerization was simulated using the periodic density functional theory. This research found that the curve between the energy barrier of ethylene polymerization and the surface energy of MgCl2 represented the volcano plot, which was consistent with the Sabatier principle. The surface energy of the support was an effective descriptor for predicting catalyst performances.

Promoting Ethylene (co)Polymerization in Aliphatic Hydrocarbon Solvents Using tert‐Butyl Substituted Nickel Catalysts

Comprehensive SummaryIn the past few decades, the development of high‐performance catalysts has been a key driving force and a center of research efforts in the field of olefin polymerization. However, a major discrepancy exists between industrial researches which utilize aliphatic hydrocarbon solvents, and academic researches which predominantly focus the catalytic properties in aromatic solvents. In this contribution, a novel diaryl‐methyl aniline bearing eight tert‐butyl groups was prepared and subsequently transformed to four different kinds of imine‐type ligands. The corresponding nickel complexes as well as their counterparts derived from diphenyl‐methyl aniline without the tert‐butyl groups were prepared and investigated in ethylene polymerization. The multiple tert‐butyl groups enable great solubility of the metal complexes in aliphatic hydrocarbon solvents, leading to similar polymerization properties comparing with aromatic solvents. In contrast, their counterparts without tert‐butyl groups demonstrate significant solvent effect. Moreover, the ligand electronic and steric effects induced by the tert‐butyl groups lead to nickel catalysts with great thermal stability (up to 140 oC) and capabilities of generating high molecular weight polymer and copolymer products. This tert‐butyl strategy can be potentially applied to many different polymerization catalyst systems and help to bridge academic studies with practical applications.

α-Diimine Ni-Catalyzed Ethylene Polymerizations: On the Role of Nickel(I) Intermediates

Nickel(II) complexes with bidentate N,N-α-diimine ligands constitute a broad class of promising catalysts for the synthesis of branched polyethylenes via ethylene homopolymerization. Despite extensive studies devoted to the rational design of new Ni(II) α-diimines with desired catalytic properties, the polymerization mechanism has not been fully rationalized. In contrast to the well-characterized cationic Ni(II) active sites of ethylene polymerization and their precursors, the structure and role of Ni(I) species in the polymerization process continues to be a “black box”. This perspective discusses recent advances in the understanding of the nature and role of monovalent nickel complexes formed in Ni(II) α-diimine-based ethylene polymerization catalyst systems.

Ti(IV)-silyliminophenolate catalysts for ϵ-caprolactone and L-Lactide polymerization

In this study, titanium (IV) silyliminophenolate complexes were synthesized by reactions of titanium (IV) isopropoxide with silyliminophenolate (SPIMPH2), and its 3-methoxy, 4-hydroxy, 5-bromo, 4-methyl, and 3-tert-butyl derivatives in isopropanol, respectively. The structures of compounds were elucidated by spectroscopic (FTIR, 1H, and 13C NMR) studies, thermal analysis (elemental and thermogravimetric), and mass spectrometry. Titanium (IV) silyliminophenolate complexes together with or without 9-anthracenemethanol (9-AnOH) are active catalyst systems for the ring-opening polymerization of ε-caprolactone (ε-CL) and L-lactide (LLA). Titanium complexes as catalysts showed moderate activity with 10–100% conversion of ε-caprolactone, L-lactide and co-monomers of ε-CL/LLA depending on temperatures, times, and the substituents on the iminophenol moiety. In addition to spectroscopic methods, gel permeation chromatography (GPC) was also used in the characterization of resulting polymers (PCL, PLLA, and Co-PCL/PLLA).

Recent developments of stereoselective ring-opening polymerization of lactides

Polylactide (PLA), derived from renewable recourses, is a kind of important materials with biodegradable and biocompatible properties, which has wide applications in the fields of biomedicine, pharmacy and environment. PLA is commonly obtained from ring-opening polymerization of lactide (LA), which has three kinds of stereo-isomers, (L)-LA, (D)-LA and meso -LA. Since PLA’s stereochemistry plays a decisive role in the thermodynamic and mechanical properties of the materials, it is an important topic to prepare stereospecific catalysts for different PLA architectures. Nowadays, significant progress has been made in the fields of single active site catalyst systems for stereoselective ring-opening polymerization of lactides. Based on our group’s work, this paper discusses the effects of metal complexes on the stereoselective polymerization of lactides, including metal center types and ligand structures.

N-Heterocyclic olefins and thioureas as an efficient cooperative catalyst system for ring-opening polymerization of δ-valerolactone

An organocatalytic ring-opening polymerization of δ-valerolactone has been developed.

EPR spectroscopic study of Ni(I) species in the catalyst system for ethylene polymerization based on α-diimine Ni(II) complex activated by MMAO

Using EPR spectroscopy, nickel(I) species formed in the catalyst system 1/MMAO for ethylene polymerization has been investigated (1 = LNiBr2, L = 1,4-bis-2,4,6-dimethylphenyl-2,3-dimethyl-1,4-diazabuta-1,3-dien). It has been shown that diamagnetic cationic complex [LNiII-tBu]+[MeMMAO]– (2) persists in system 1/MMAO at low temperatures, but rapidly decays at 25 °C to give new EPR active species 3 (major product) and 4 (minor product). Species 3 is a nickel(I) complex with the proposed structure [LNiI(S)]+[MeMMAO]– (S = solvent), whereas 4 is L(•−)AlMe2 species. Upon the addition of ethylene, complex 3 partially reversibly converts into the adduct [LNiI(C2H4)]+[MeMMAO]– (5). After ethylene consumption, species 3 restores its original concentration.

HNTs/GO composite as efficient catalyst for ring-opening polymerization of ε-Caprolactone

ABSTRACTPolycaprolactone (PCL) has been widely applied based on the biocompatibility and biodegradability. It is important to investigate the safe and efficient catalyst system for ring-opening polymerization of monomer ε-caprolactone (ε-CL). In our work, Halloysite/Graphene Oxide (HNTs/GO) composite is successfully prepared by electrostatic self-assembly and used as an effective catalyst for the ring-opening polymerization of ε-CL. The structures, morphologies and thermal properties of the products are subsequently characterized. The results show that the synthesized PCL are semi-crystalline and observed to be lamellar, which depend on the template effects of HNTs/GO composite. The HNTs/GO composite serves as an effective catalyst and a reinforcing filler simultaneously to improve the thermal stability of the prepared PCL.

Cationic acetylacetonate palladium complexes/boron trifluoride etherate catalyst systems for polymerization of 5-methoxycarbonylnorbornene

A simple protocol using cationic acetylacetonate palladium complexes with mono-/bidentate phosphine ligands activated with BF3·OEt2 as in situ-formed catalyst for polymerization of endo/exo mixture of 5-methoxycarbonylnorbornene (activity up to 1.1·104gmol−1h−1) or 5-phenylnorbornene (7.2·105gmol−1h−1), and norbornene (3.3·108gmol−1h−1) have been developed. It was observed that the ligands nature strongly influence the catalytic activity. The catalyst system Pd(II)/BF3·OEt2 was also active for the copolymerization of norbornene with 5-methoxycarbonylnorbornene. DFT calculations of isomers upon single insertion of 5-methoxycarbonylnorbornene into PdH bond and NMR/FTIR studies for pre-catalyst activation mechanism were performed.

Catalyst system for olefin polymerization and method for producing olefin polymer

Copper nanoparticles show considerable antibacterial, anti-fungal and related effects in comparison with bulk CuO and have been explored for their biological applications. In this work green synthesis approach was adopted to synthesize CuONps utilizing Syzygium aromaticum bud extract. CuONps showed a sharp band around 298 nm in UV–Vis spectrum, affirming their formation. The average size of synthesized CuONps was inspected by Debye-Scherrer equation using PXRD spectrum and was found 70 nm. Interaction study of CuONps with Calf-Thymus DNA have been investigated which has given significant results. The CuONps have also shown 20% DNA cleavage activity against E.coli DNA.

Polymers for catalysis in water purification

This review highlights the application of polymeric material in catalyst system for water purification technologies. Insufficient access to safe and clean drinking water is one of the most demanding needs of the people throughout the world. The consequences are death casualty of millions of people annually, mostly under the age of 5, by the diseases transmitted through contaminated water or human. Recent, flare‐up growth of polymeric technologies offers to handle such water purification as an adsorbent, catalyst, and sensors. This is due to its high reactivity, selectivity, and specific surface area. The nanocatalyst loaded polymeric system has been applied for the selective and efficient removal of pollutants from aqueous sources and demonstrated a highly resistant against mechanical stress, high temperature, pressure, and solvents. Different techniques including membrane technology, photocatalyst, and adsorbent have provided a medium for the polymeric catalyst. These series of metal oxide photocatalyst have been applied for several types of polymers including polysulfonate, poly(ether) sulfone, polyvinyl acetate, stract, polyurethane, and polyamide. It recorded that, the polymeric catalyst system is frequently utilized without loss of their specific adsorption and catalytic properties. The combined effects of water chemistry, nature of catalyst particles, loading capacity, and catalyst incorporation conditions for each system have been discussed in details.