Catalytic Polymerization Research Articles

Mono- and bi-nuclear phosphine-phenolate neutral nickel catalysts via simple Schiff-Base condensation for ethylene polymerization

In catalytic olefin polymerization, a significant amount of effort has been invested to modify either phosphine substituent or ligand backbone in recently advanced phosphine-phenolate [P,O] neutral nickel catalysts. Unlike other commonly used ligands like phenoxy-imines [N,O] and α-diimines [N,N], [P,O] ligands often require a laborious synthesis technique, which has hindered the rational design of ligand structures and the development of new catalysts. Here we present a novel and effective strategy for creating catalysts using [N,O,P] hybrid ligands. The substituent adjacent to the phenoxy group can be efficiently modified through straightforward Schiff-base condensation reactions with various amines that have established synthetic routes and diverse structures. This process results in the preparation of a series of highly active [P,O] nickel catalysts (up to 1.7 × 107 g mol-1h−1) that are capable of producing ultrahigh molecular weight polyethylene (UHMWPE) (Mw = 243.7 × 104 g/mol) in ethylene polymerization. The additional binding site greatly facilitates modulation of catalytic properties by additives, and parameters such as catalytic activity, polymer molecular weight, and polymer branching can be tuned in this way. Furthermore, binuclear [P,O] neutral nickel catalysts for olefin polymerization are synthesized for the first time using a sequence of diamines. The strategy presented in this work greatly improves the efficiency for the design and synthesis of [P,O] nickel and related catalysts. These findings will be advantageous for future catalyst design and screening.

In situ catalytic polymerization of LiNO3-containing PDOL electrolytes for high-energy quasi-solid-state lithium metal batteries

1,3-Dioxolane (DOL) can be induced to form polymer electrolytes by in situ ring opening polymerization at Lewis acid salts. However, the presence of ion–dipole interactions between NO3− and DOL suppresses this polymerization behavior. Herein, we report that the use of Sc(OTf)3 as an initiator can well disrupt this ion–dipole interaction. The in situ ring-opening polymerization of DOL is achieved to form a LiNO3-modified polyDOL-based electrolyte. New mechanism of Li migration in polymer electrolytes have been revealed by molecular dynamics modeling and constructed molecular interface models. It is found that the electrolyte interior is affected by the ion–dipole interactions of Li+ by NO3−, which made it easier for Li+ to be released from the polar ether-oxygen ligands on the polymer chain for rapid migration, thus exhibiting an ionic conductivity of 1.8 mS cm−1 and tLi+ of 0.78. In addition, NO3− preempts the binding sites around Li+, improves the coordination environment, and prioritizes the formation of a kinetically stable anion-derivative interface, which effectively mitigates the interfacial side reactions between the electrodes and the electrolytes. As a result, the assembled solid-state Li||LiFePO4 cell exhibits an impressive 152.3 mAh/g discharge capacity at 0.5C and maintains 80.3 % of the capacity after 450 cycles at 50 °C. This work not only opens a new avenue for designing high-performance gel polymer electrolytes for more metal-based batteries, but also provides valuable insights into understanding the ion migration mechanism.

Donor Ability of Bisphosphinemonoxide Ligands Relevant to Late-Metal Olefin Polymerization Catalysis.

Late-transition-metal catalysts for polymerization of olefins have drawn a significant amount of attention owing to their ability to tolerate and incorporate polar comonomers. However, a systematic way to experimentally quantify the electronic properties of the ligands used in these systems has not been developed. Quantified ligand parameters will allow for the rational design of tailored polymerization catalysts, which would target specific polymer properties. We report a series of platinum complexes bearing bisphosphinemonoxide ligands, which resemble those used in the polymerization catalysts of Nozaki and Chen. Their electronic properties are investigated experimentally, and trends are rationalized by using computed spectral properties. Benchmarking computational data with known experimental parameters further enhances the utility of both methods for determining optimal ligands for catalytic application.

Slippery Core‐Sheath Hydrogel Optical Fiber Built by Catalytically Triggered Interface Radical Polymerization

AbstractHydrogel‐based optical waveguides have attracted extensive attention in optogenetics, implantable photomedicine, and biosensors due to their excellent biocompatibility and tissue‐like modulus in compared with traditional SiO2‐based rigid optical fibers. However, the existing ion‐induced supramolecular assembly of alginate‐based hydrogel optical fibers commonly lack of long‐term stability due to poor mechanical property accompanied with swollen. In this paper, a novel catalytic surface polymerization method is developed based on a redox reaction mechanism to in situ grow robust and slippery cladding layer on a core poly(ethylene glycol) dimethacrylate (PEGDA) hydrogel fiber by using the alternative H‐bonding poly(N ‐acryloyl glycinamide) (PNAGA) hydrogels. The resultant hydrogel optical fiber with core‐cladding heterogeneous structure can achieve the desirable total reflection condition, leading to good light transmission and low light loss. The PNAGA cladding with robust H‐bonding network endows the hydrogel optical fiber with high stability and outstanding lubrication in humid environment. More importantly, the hydrogel optical fiber possesses good tissue‐like mechanical performance together with excellent biocompatibility, which shows the great advantages for biomedical applications in compared with traditional glass optical fibers. This work will broaden implantable hydrogel optical fibers in material design and structure processibility, promoting the use of hydrogel‐based optical fibers in various applications.

Vat photopolymerization using catalytic chain transfer polymerization (CCTP) derived reactive oligomers to influence mechanical properties

ω-Vinyl terminated reactive oligomers of 2-ethylhexyl methacrylate and poly(ethylene glycol)methacrylate (PEGMA) were synthesized via CCTP and subsequent addition–fragmentation chain transfer (AFCT) polymerization.

Heterogenous catalysis for oxygen tolerant photoredox atom transfer radical polymerization and small-molecule dehalogenation

Heterogeneous photocatalysts (PCs) have garnered attention for their sustainability and cost-effectiveness.

Bis-[C(sp3)-chelating] Ti2 catalysts supported by arylene-1,4-diyl-2,3-X2 bridges for olefin copolymerisation: X substituents impose conformational cooperative effects.

The synthesis, spectroscopic characterisation and catalytic olefin polymerisation behaviour of a class of binuclear titanium bis(benzyl) complexes bearing bis-(pyridine-2-phenolate-6-methine)-[μ-(arylene-1,4-diyl-2,3-X2)] ligands [X2 = -C4H4- (1), F2 (2), H2 (3)], and mononuclear analogues, are described. These bimetallic catalyst frameworks are designed to exhibit a degree of conformational flexibility, which is regulated by steric effects and crucially permits tuning of intermetallic distances and geometry, yet their shape-persistent nature can also confer favourable entropic terms. Complexes 1-3 are characterised as two diastereomers [meso (RS) and rac (RR,SS)] in ratios of 1.32, 1.18 and 1.13 respectively, according to 1H NMR spectroscopy. In contrast to 3, [1H,1H]-ROESY experiments for 1 and 2 revealed that the X2 substituents can impose preferred conformations with syn orientations of Ti2 centres and benzyl groups, thus implying that the activated catalysts would present binding sites with the same direction of access. For ethylene-(1-octene) copolymerisation reactions, in conjunction with [Ph3C][B(C6F5)4], catalyst 1 displayed superior efficiencies and produced polymers with higher Mw values and enhanced comonomer incorporation ratios (up to 41%), when compared with the mononuclear 5m (22%). These results are indicative of enhanced comonomer enchainment and cooperative reactivity by the Ti2 sites.

Bimetallic nickel complexes containing imidazole-based phenolate ligands as efficient catalysts for the copolymerization of carbon dioxide with epoxides.

The utilization of hexadentate imidazole-derived diamine-bisphenolate ligands to construct structurally well-defined bimetallic nickel catalysts that enable the mediation of the copolymerization of carbon dioxide with alicyclic epoxides was reported for the first time. A series of dinickel carboxylate/nitrophenolate complexes were facilely prepared through a one-pot procedure and their structures were fully determined by single crystal X-ray structural analysis. Dinickel complexes 1-10 were used as single-component catalysts, and were evaluated for the copolymerization of CO2 and cyclohexene oxide (CHO), for which acetato-incorporated complex 1 was proved to exhibit the best activity. Not only has the controllability of binickel catalyst 1 for CO2/CHO copolymerization been demonstrated, but also an "immortal" character for the same polymerization has been realized. Furthermore, detailed kinetic studies of polymerization catalysis of this type were undertaken, and the kinetics results revealed a first-order dependence on both Ni complex 1 and CHO concentrations. This is a successful example of the introduction of the easily accessible nitrogen-heterocycle group, the imidazole moiety, into phenolate ligands for the development of high-performance homogeneous catalysts towards the bimetallic complex-catalyzed copolymerization of CO2 and epoxides.

Easy access to amphiphilic nitrogenous block copolymers via switchable catalysis.

A key challenge in polymer synthesis is to develop new methods that enable block copolymers to be prepared from mixed monomer feedstock. The emerging switchable polymerization catalysis can generate block copolymers with well-defined structures and tunable properties from monomer mixtures. However, constrained by the reactivity of monomers and the incompatibility of different polymerization mechanisms, this method is usually confined to oxygenated monomers. In this work, the switchable polymerization was successfully applied to nitrogenous monomers for the first time, achieving the efficient copolymerization of N-substituted N-carboxyanhydrides (NNCAs) with epoxides and cyclic anhydrides. This leads to easy access towards amphiphilic nitrogenous copolymers, such as polyester-b-polypeptoids. Density functional theory calculations demonstrated that the reaction of cyclic anhydrides with the alkoxide terminal is thermodynamically more favorable than that of NNCAs. Characterization, using nuclear magnetic resonance spectroscopy, size exclusion chromatography and in situ infrared spectroscopy, has confirmed the well-defined block structure of the obtained copolymers. This switchable polymerization strategy is applicable to a range of monomer mixtures with different oxygenated monomers and NNCAs, providing a highly efficient synthetic route towards nitrogenous block copolymers. Most importantly, the easily accessed amphiphilic polyester-b-polypeptoids demonstrated excellent anti-protein adsorption capabilities and barely any cytotoxicity, showing great potential in the field of biomedicine.

Theoretical investigations of 2-vinylpyridine stereoselective polymerization catalyzed by cationic yttrium complexes with different ancillary ligands.

The polymerization mechanism of 2-vinylpyridine catalyzed by cationic yttrium complexes with diverse ancillary ligands, specifically [L1Y(CH2SiMe3)(THF)]+ [L1 = (2,6-Et2C6H3)NC(Me)CHC(Me)N(2,6-Et2C6H3)] (Y-1), [L2Y(CH2SiMe3)(THF)]+ [L2 = (2,6-Cl2C6H3)NC(Me)CHC(Me)N(2,6-Cl2C6H3)] (Y-2), and [L3Y(CH2SiMe3)(THF)]+ [L3 = (2,6-C6H5)NC(Me)CHC(Me)N(2,6-iPr2C6H3)] (Y-3), was studied using density functional theory (DFT) calculations. Having achieved an agreement between theory and experiment, it is found that isotactic selectivity induced by Y-1 or Y-2 results from a combination of smaller deformation of the catalyst and stronger electronic effects. Conversely, the Y-3 complex exhibits comparable energy barriers for proceeding via either isotactic or syndiotactic pathways, aligning with the production of atactic polymers as seen experimentally. To examine the steric effects on the kinetic and thermodynamic properties, a computational model of an analogue complex [L4Y(CH2SiMe3)(THF)]+ [L4 = (2,6-Cl2C6H3)NC(Me)CHC(Me)N(iPr2C6H3)] (Y-4), featuring increased steric hindrance, was analyzed. Distortion-interaction and topographic steric map analyses further affirmed that steric hindrance significantly influences stereoselectivity. A direct relationship was identified between the energy barriers of isotactic insertion transition states and the bulkiness of ancillary ligands; greater distortion energy of the catalyst correlates with higher barriers for isotactic polymerization. These findings enhance the mechanistic comprehension of 2-vinylpyridine polymerization and are expected to contribute valuable insights for the improvement of catalytic polymerization systems of 2-vinylpyridine.

Catalytic polymerization of isoprene using an ultrahigh active iron(ii) complex with an ortho-modified 1,10-phenanthroline ligand, access to a thermal plastic rubber

Bidentate N,N-ligands have played a vital role in the iron-mediated polymerization of 1,3-diene over the past few decades.

Catalytic Ring-Opening Polymerisation of Cyclic Ethylene Carbonate: Importance of Elementary Steps for Determining Polymer Properties Revealed via DFT-MTD Simulations Validated Using Kinetic Measurements.

The production of CO2-containing polymers is still very demanding in terms of controlling the synthesis of products with pre-defined CO2 content and molecular weight. An elegant way of synthesising these polymers is via CO2-containing building blocks, such as cyclic ethylene carbonate (cEC), via catalytic ring-opening polymerisation. However, to date, the mechanism of this reaction and control parameters have not been elucidated. In this work, using DFT-metadynamics simulations for exploiting the potential of the polymerisation process, we aim to shed more light on the mechanisms of the interaction between catalysts (in particular, the catalysts K3VO4, K3PO4, and Na2SnO3) and the cEC monomer in the propagation step of the polymeric chain and the occurring CO2 release. Confirming the simulation results via subsequent kinetics measurements indicates that, depending on the catalyst's characteristics, it can be attached reversibly to the polymeric chain during polymerisation, resulting in a defined lifetime of the activated polymer chain. The second anionic oxygen of the catalyst can promote the catalyst's transfer to another electrophilic cEC monomer, terminating the growth of the first chain and initiating the propagation of the new polymer chain. This transfer reaction is an essential step in controlling the molecular weight of the products.

Improvement in BHETA yield by aminolysis and its application in hot melt adhesive

Polyethylene terephthalate (PET) recycling has been carried out by various methods, e.g., mechanical recycling, chemical recycling, and energy recovery method. In this study, chemical recycling of PET was carried out by aminolysis using ethanolamine and converted into bis(2-hydroxyethyl) terephthalamide (BHETA). We have studied the effective polymeric catalysis of the aminolytic depolymerization of waste polyethylene terephthalate (PET) using sulfated polyborate producing a broad range of crystalline terephthalamides. The reaction was performed by varying the PET: ethanolamine ratio, reaction time and catalyst. Recycled PET bottles, film, and fibres were used for conversion. A yield of 95 % was obtained for PET: ethanolamine ratio of 1:4 (w/w), with 4 h reaction time, at 160oC with sulfated polyborate as a catalyst. BHETA was characterized with FTIR, 1H,13C NMR, and DSC analysis. BHETA further gets reacted with dimer acid along with Ethylenediamine (EDA) at different molar ratios which produces polyesteramide (PEA) based hot melt adhesive (HMA). Thermal, mechanical, and rheological tests are performed and compared with traditional HMA. The effect on the properties of the hot melt adhesive, such as mechanical properties: tensile strength, shore D hardness, elongation at break; thermal properties: glass transition temperature (Tg), melting temperature (Tm), the heat of crystallization (Hc), crystallization temperature (Tc); adhesion properties: lap shear strength (LSS) and T-peel strength (TPS); rheological properties and degree of crystallinity were investigated. It was observed that the mechanical and thermal properties are increased by optimizing the concentration of BHETA. These HMA materials may have the capacity of being eco-friendly and have high adhesion properties.

Catechol-formaldehyde resin microspheres@UiO-66-NH2@ CdS core-shell nanohybrids as robust visible-light photocatalyst for multifunctional applications

Well-defined zirconium based metal-organic frameworks (MOFs) coated polymer core-shell nanohybrid (CFR@MOF) was constructed using catechol formaldehyde resin (CFR) microspheres as a support, followed by encapsulating CdS nanoparticles (NPs) into MOF (UiO-66-NH2) shell layers to obtain CFR@UiO-66-NH2@CdS nanohybrids to enhance visible photosensitization for multifunctional photocatalytic applications including organic pollutant degradation, water disinfection and photoinduced atomic transfer radical polymerization (photoATRP). The CFR microspheres with a regular spherical morphology (200–400 nm) provided a versatile initial platform for the growth of MOF shells through mononuclear coating. The impact of different loadings of CdS NPs incorporated into CFR@UiO-66-NH2 shells on photocatalytic performance was systematically investigated. CFR@UiO-66-NH2 @CdS demonstrated robust dye degradation and antibacterial ability. Especially, a remarkable inhibitory efficiency of 99.99 % and 99.7 % was achieved for S. aureus and E. coli, with a low photocatalyst dosage (100 μg/mL) under visible light. Furthermore, by combining CFR@UiO-66-NH2@CdS with CuBr2/L catalysts, a high-efficiency red-light triggered photoredox catalytic polymerization system was established in photoinduced atom transfer radical polymerization (photoATRP), achieving high conversion rate (>90 %) for various monomers in a short time.

Parallel Catalyst Synthesis Protocol for Accelerating Heterogeneous Olefin Polymerization Research.

The data scientific approach has become an indispensable tool for capturing structure-performance relationships in complex systems, where the quantity and quality of data play a crucial role. In heterogeneous olefin polymerization research, the exhaustive and multi-step nature of Ziegler-Natta catalyst synthesis has long posed a bottleneck in synthetic throughput and data generation. In this contribution, a custom-designed 12-parallel reactor system and a catalyst synthesis protocol were developed to achieve the parallel synthesis of a magnesium ethoxide-based Ziegler-Natta catalyst. The established system, featuring a miniature reaction vessel with magnetically suspended stirring, allows for over a tenfold reduction in synthetic scale while ensuring the consistency and reliability of the synthesis. We demonstrate that the established protocol is highly efficient for the generation of a catalyst library with diverse compositions and physical features, holding promise as a foundation for the data-driven establishment of the structure-performance relationship in heterogeneous olefin polymerization catalysis.

Operando spectroscopies and heterogeneous olefin polymerization catalysis: A rare marriage with a lot of potential beyond usual understanding

This short review summarizes the main results achieved in the field of operando spectroscopies applied to heterogeneous catalysts for olefin polymerization. Following a chronological order, starting from the first spectroscopic measurements applied to the Phillips catalyst, the review retraces the main stages of this exciting story, reporting also some details on the experimental set-ups adopted from time to time, the difficulties encountered, the failures, and the solutions taken to address the problems. What emerges is a dynamic picture with still many unexplored potentialities, even though unfortunately limited to a few research groups systematically engaged in this field.

What Can Industrial Catalytic Olefin Polymerization Plants Tell Us About Reaction Kinetics? From Production Rate and Residence Time to Catalyst Reaction Performance.

AbstractThe information available in daily plant operation data is not fully exploited by polymer reaction engineers: what do the catalytic olefin polymerization plants tell? In this article, a method is proposed to increase catalyst and process know‐how, based on experimentally acquired production rate results, coming from a continuous tandem reactor polymerization process. The polymer reaction engineering methodology is also discussed in detail for connecting the catalyst reaction performance to the expected activity profile and yield for batch operation, together with the residence time distribution effect for continuous operation. The potential of the proposed methodology is highlighted with a theoretical example and the effectiveness of the method is demonstrated with an applied example, accurately estimating deactivation parameter values for two catalysts based on plant information and, validated based on small‐scale polymerization experiments.

Nopadiene: A Pinene-Derived Cyclic Diene as a Styrene Substitute for Fully Biobased Thermoplastic Elastomers.

The bicyclic 1,2-substituted, 1,3-diene monomer nopadiene (1R,5S)-2-ethenyl-6,6-dimethylbicyclo[3.1.1]hept-2-ene was successfully polymerized by anionic and catalytic polymerization. Nopadiene is produced either through a facile one-step synthesis from myrtenal via Wittig-olefination or via a scalable two-step reaction from nopol (10-hydroxymethylene-2-pinene). Both terpenoids originate from the renewable β-pinene. The living anionic polymerization of nopadiene in apolar and polar solvents at 25 °C using organolithium initiators resulted in homopolymers with well-controlled molar masses in the range of 5.6-103.4 kg·mol-1 (SEC, PS calibration) and low dispersities (Đ) between 1.06 and 1.18. By means of catalytic polymerization with Me4CpSi(Me)2NtBuTiCl2 and (Flu)(Pyr)CH2Lu(CH2TMS)2(THF), the 1,4 and 3,4- microstructures of nopadiene are accessible in excellent selectivity. In pronounced contrast to other 1,3-dienes, the rigid polymers of the sterically demanding nopadiene showed an elevated glass temperature, Tg,∞ = 160 °C (in the limit of very high molar mass, Mn). ABA triblock copolymers with a central polymyrcene block and myrcene content of 60-75 mol %, with molar masses of 100-200 kg/mol were prepared by living anionic polymerization of the pinene-derivable monomers nopadiene and myrcene. This diene copolymerization resulted in thermoplastic elastomers displaying nanophase separation at different molar ratios (DSC, SAXS) and an upper service temperature about 30 K higher than that for traditional petroleum-derived styrenic thermoplastic elastomers due to the high glass temperature of polynopadiene. The materials showed good thermal stability at elevated temperatures under nitrogen (TGA), promising tensile strength and ultimate elongation of up to 1600%.

Evaluating Heterodinuclear Mg(II)M(II) (M = Mn, Fe, Ni, Cu, and Zn) Catalysts for the Chemical Recycling of Poly(cyclohexene carbonate).

Polymer chemical recycling to monomers (CRM) is important to help achieve a circular plastic economy, but the "rules" governing catalyst design for such processes remain unclear. Here, carbon dioxide-derived polycarbonates undergo CRM to produce epoxides and carbon dioxide. A series of dinuclear catalysts, Mg(II)M(II) where M(II) = Mg, Mn, Fe, Co, Ni, Cu, and Zn, are compared for poly(cyclohexene carbonate) depolymerizations. The recycling is conducted in the solid state, at 140 °C monitored using thermal gravimetric analyses, or performed at larger-scale using laboratory glassware. The most active catalysts are, in order of decreasing rate, Mg(II)Co(II), Mg(II)Ni(II), and Mg(II)Zn(II), with the highest activity reaching 8100 h-1 and with >99% selectivity for cyclohexene oxide. Both the activity and selectivity values are the highest yet reported in this field, and the catalysts operate at low loadings and moderate temperatures (from 1:300 to 1:5000, 140 °C). For the best heterodinuclear catalysts, the depolymerization kinetics and activation barriers are determined. The rates in both reverse depolymerization and forward CHO/CO2 polymerization catalysis show broadly similar trends, but the processes feature different intermediates; forward polymerization depends upon a metal-carbonate intermediate, while reverse depolymerization depends upon a metal-alkoxide intermediate. These dinuclear catalysts are attractive for the chemical recycling of carbon dioxide-derived plastics and should be prioritized for recycling of other oxygenated polymers and copolymers, including polyesters and polyethers. This work provides insights into the factors controlling depolymerization catalysis and steers future recycling catalyst design toward exploitation of lightweight and abundant s-block metals, such as Mg(II).

MnFe2O4 composited polyvinylidene fluoride catalytic ultrafiltration membrane via peroxymonosulfate activation for humic acid treatment: Exploration of synergistic mechanisms

Membrane separation has become the most promising technology in the field of wastewater purification, but there will inevitably be membrane fouling. Catalytic polymer membranes combining membrane filtration and advanced oxidation technologies (AOPs) offered an alternative for mitigating membrane fouling. This work successfully synthesized a MnFe2O4 catalytic polyvinylidene fluoride (MnFe2O4-PVDF) ultrafiltration membrane and systematically investigated the performance of peroxymonosulfate (PMS)/MnFe2O4 membrane oxidation filtration system for removing humic acid (HA). The results showed that the PVDF@MnFe2O4/PMS synergistic system oxidized HA into small molecules and further repelled them to the membrane surface by size exclusion to form a filter cake layer. The PVDF@MnFe2O4/PMS system exhibited the lowest irreversible fouling (0.414 × 1010m−1) and the highest HA removal efficiency (83.4 %) compared with PVDF single filtration. After hydrodynamic cleaning, PVDF@MnFe2O4 can achieve 73.2 % water flux recovery. The membrane fouling mitigation mechanisms were investigated by the Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory and the combined pore blockage-cake filtration model. Quenching experiment and density functional theory calculation (DFT) revealed the HA degradation as a result of the synergistic action of free radicals (SO4⋅-, ⋅OH) and non-free radicals(1O2) in PVDF@MnFe2O4/PMS system. Additionally, we evaluated the effectiveness of the system in the removal of natural organic matter (NOM) from surface water. The results suggested that the PVDF@MnFe2O4/PMS system could validly remove the main fluorescent matters from surface water. In conclusion, this work provides a promising route for solving the membrane fouling caused by NOM in water.