Insertion Polymerization Research Articles

Enhancing electrical conductivity in zirconium-doped SiC ceramics through synergistic effects of crystal structure and free carbon control.

Polymer-derived ceramics (PDCs) have risen to prominence for applications in electrochemical energy storage, electromagnetic absorbing, and sensing materials, among others. However, a multitude of critical properties in PDCs are still limited by their intrinsic poor electrical conductivity. Herein, novel vinyl and zirconium-modified polycarbosilane precursors with improved electrical conductivity were synthesized through a Grignard coupling reaction of vinyl magnesium chloride and zirconocene dichloride, followed by the insertion polymerization with dichlorodimethylsilane and sodium. Our findings reveal a complex structural evolution from amorphous ZrO2 to distinct phases like m-ZrO2, t-ZrO2, and ZrC. This transformation significantly impacts the distribution and morphology of free carbon ribbons, influencing the material conductive network and resulting in an enhanced electrical conductivity of 0.28 S cm-1 and reduced bandgap. Through density functional theory analysis, a unique interaction between the energy bands of the carbon ribbons and the native cell is discovered, leading to a narrowed energy bandgap and conductive behavior. This advancement not only offers insight into the material structure-conductivity relationship but also opens new avenues for applications such as lithium battery anodes.

Concerted flexible and steric strategy in α-diimine nickel and palladium mediated insertion (Co-)Polymerization

To address the issues of poor thermostability of catalyst and low polymer molecular weight resulted from chain transfer at high temperature in olefin polymerization, versatile strategies have been utilized in the benchmark α-diimine nickel and palladium catalysts. In this contribution, a concerted flexible and steric strategy was highlighted in the α-diimine nickel and palladium catalysts. Compared to the seminal Brookhart catalyst, these newly generated nickel catalysts exhibited improved thermostability over a wide range of temperature from 30 °C to 130 °C, showed higher catalytic activities, and produced significantly higher (4.7–5.8 times) molecular weight polymers in ethylene polymerization, which are highly branched polyethylenes (76–110/1000C, SR = 72 %). Notably, high molecular weight polyethylene (up to 219 kg mol−1) was even afforded at 130 °C, which is extremely challenging when the flexible substituent is used in α-diimine system. The corresponding palladium analogues by using the same strategy further produced high molecular weight ethylene-methyl acrylate copolymers (up to 137 kg mol−1) at the difficult 70 °C in the copolymerization of ethylene and methyl acrylate. The incorporation of methyl acrylate could be tuned (0.6–2.9 mol%), where methyl acrylate units distribute both in the main chain and at the end of branches (15 %:85 %).

Facile Synthesis of Linear and Cyclic Poly(diphenylacetylene)s by Molybdenum and Tungsten Catalysis.

Improved methods for the synthesis of linear and cyclic poly(diphenylacetylene)s by polymerization of the corresponding diphenylacetylenes using MoCl5 - and WCl4 -based catalytic systems have been developed. MoCl5 induces migratory insertion polymerization of diphenylacetylenes in the presence of arylation reagents such as Ph4 Sn and ArSnn Bu3 to produce cis-stereoregular linear poly(diphenylacetyelene)s with high molecular weights (number-average molar mass (Mn )=30,000-3,200,000) in good yields (up to 98 %). On the other hand, WCl4 induces ring expansion polymerization of diphenylacetylenes in the presence of Ph4 Sn or reducing reagents to produce cis-stereoregular cyclic poly(diphenylacetylene)s with high molecular weights (Mn =20,000-250,000) in moderate to good yields (up to 90 %). Both catalytic systems are applicable to the polymerization of various diphenylacetylenes having polar functional groups such as esters that are not efficiently polymerized by conventional methods using WCl6 -Ph4 Sn and TaCl5 -n Bu4 Sn systems.

Facile Synthesis of Linear and Cyclic Poly(diphenylacetylene)s by Molybdenum and Tungsten Catalysis

AbstractImproved methods for the synthesis of linear and cyclic poly(diphenylacetylene)s by polymerization of the corresponding diphenylacetylenes using MoCl5‐ and WCl4‐based catalytic systems have been developed. MoCl5 induces migratory insertion polymerization of diphenylacetylenes in the presence of arylation reagents such as Ph4Sn and ArSnnBu3 to produce cis‐stereoregular linear poly(diphenylacetyelene)s with high molecular weights (number‐average molar mass (Mn)=30,000–3,200,000) in good yields (up to 98 %). On the other hand, WCl4 induces ring expansion polymerization of diphenylacetylenes in the presence of Ph4Sn or reducing reagents to produce cis‐stereoregular cyclic poly(diphenylacetylene)s with high molecular weights (Mn=20,000–250,000) in moderate to good yields (up to 90 %). Both catalytic systems are applicable to the polymerization of various diphenylacetylenes having polar functional groups such as esters that are not efficiently polymerized by conventional methods using WCl6‐Ph4Sn and TaCl5‐nBu4Sn systems.

Direct Insertion Polymerization of Ionic Monomers: Rapid Production of Anion Exchange Membranes

AbstractThe limited number of methods to directly polymerize ionic monomers currently hinders rapid diversification and production of ionic polymeric materials, namely anion exchange membranes (AEMs) which are essential components in emerging alkaline fuel cell and electrolyzer technologies. Herein, we report a direct coordination‐insertion polymerization of cationic monomers, providing the first direct synthesis of aliphatic polymers with high ion incorporations and allowing facile access to a broad range of materials. We demonstrate the utility of this method by rapidly generating a library of solution processable ionic polymers for use as AEMs. We investigate these materials to study the influence of cation identity on hydroxide conductivity and stability. We found that AEMs with piperidinium cations exhibited the highest performance, with high alkaline stability, hydroxide conductivity of 87 mS cm−1 at 80 °C, and a peak power density of 730 mW cm−2 when integrated into a fuel cell device.

Direct Insertion Polymerization of Ionic Monomers: Rapid Production of Anion Exchange Membranes.

The limited number of methods to directly polymerize ionic monomers currently hinders rapid diversification and production of ionic polymeric materials, namely anion exchange membranes (AEMs) which are essential components in emerging alkaline fuel cell and electrolyzer technologies. Herein, we report a direct coordination-insertion polymerization of cationic monomers, providing the first direct synthesis of aliphatic polymers with high ion incorporations and allowing facile access to a broad range of materials. We demonstrate the utility of this method by rapidly generating a library of solution processable ionic polymers for use as AEMs. We investigate these materials to study the influence of cation identity on hydroxide conductivity and stability. We found that AEMs with piperidinium cations exhibited the highest performance, with high alkaline stability, hydroxide conductivity of 87 mS/cm at 80 °C, and a peak power density of 730 mW/cm2 when integrated into a fuel cell device.

A metal-free and air-tolerable insertion polymerization using sulfoxonium ylides as monomers

Insertion polymerization represents a concise approach to construct carbon-heteroatom bonds in the main chain. Despite some momentous efforts have been devoted to transition-metal catalyzed insertion polymerization, the metal-free insertion polymerization remains elusive. Herein, the fascinating metal-free and air-tolerable insertion polymerization using sulfoxonium ylides as monomers has been disclosed, furnishing a plethora of polythioethers and aromatic polyamines with carbon-heteroatom bonds in the main chain (yield up to 99%, Mn up to 20100). The insertion polymerization features mild condition, easy operation and broad substrate scope. In addition, thermal analysis demonstrated the polymers exhibited good thermal properties.

Cover Picture: One‐For‐All Polyolefin Functionalization: Active Ester as Gateway to Combine Insertion Polymerization with ROP, NMP, and RAFT (Angew. Chem. Int. Ed. 33/2022)

A polyolefin active ester exchange (PACE) process was developed for polyolefin-containing block copolymer synthesis and serves as a bridge connecting coordination–insertion polymerization to multiple controlled polymerization methods. As reported by Krzysztof Matyjaszewski, Eva Harth et al. in their Research Article (e202205931), PACE allows for the synthesis of hybrid materials that comprise olefins and ester, styrene, vinylic, acrylate, and acrylamide segments with a broad window for tunability. Nano-objects with higher-order morphologies can be obtained directly via RAFT-mediated PISA.

Titelbild: One‐For‐All Polyolefin Functionalization: Active Ester as Gateway to Combine Insertion Polymerization with ROP, NMP, and RAFT (Angew. Chem. 33/2022)

Ein aktiver Polyolefin-Esteraustausch (PACE) wurde für die Synthese polyolefinhaltiger Blockcopolymere entwickelt. Der Prozess verknüpft die Koordinations-Insertions-Polymerisation mit multiplen kontrollierten Polymerisationsmethoden. Wie Krzysztof Matyjaszewski, Eva Harth et al. in ihrem Forschungsartikel (e202205931) berichten, ermöglicht PACE die Synthese von Hybridmaterialien, die Olefine sowie Ester-, Styrol-, Vinyl-, Acrylat- und Acrylamidsegmente enthalten und in einem breiten Fenster gezielt abgestimmt werden können. Nanoobjekte mit Morphologien höherer Ordnung können direkt über RAFT-vermittelte PISA erhalten werden.

Molecularly Defined Polyolefin Vitrimers from Catalytic Insertion Polymerization.

Vitrimers can combine the advantageous properties of cross-linked materials with thermoplastic processability. For the prominent case of polyethylene, established post-polymerization introduction of cross-linkable moieties results in extremely heterogeneous compositions of the chains. Here, we report the generation of functionalized polyethylenes directly by catalytic insertion polymerization, with incorporated cross-linkable aryl boronic esters or alternatively acetal-protected groups suited for cross-linking with difunctional boronic esters. In addition to the desired homogeneous in-chain distribution, the reactive cross-linkable groups are enriched at the chain ends. This enables the incorporation of all chains in the network, as also supported by simulations of all chains' compositions. The uniform molecular composition of the chains reflects in resulting vitrimers' material properties, particularly lack of leaching with solvents. At the same time, cross-linking is indeed fully reversible and the vitrimers can be recycled.

One‐For‐All Polyolefin Functionalization: Active Ester as Gateway to Combine Insertion Polymerization with ROP, NMP, and RAFT

AbstractThis work develops the Polyolefin Active‐Ester Exchange (PACE) process to afford well‐defined polyolefin–polyvinyl block copolymers. α‐Diimine PdII‐catalyzed olefin polymerizations were investigated through in‐depth kinetic studies in comparison to an analog to establish the critical design that facilitates catalyst activation. Simple transformations lead to a diversity of functional groups forming polyolefin macroinitiators or macro‐mediators for various subsequent controlled polymerization techniques. Preparation of block copolymers with different architectures, molecular weights, and compositions was demonstrated with ring‐opening polymerization (ROP), nitroxide‐mediated polymerization (NMP), and photoiniferter reversible addition–fragmentation chain transfer (PI‐RAFT). The significant difference in the properties of polyolefin–polyacrylamide block copolymers was harnessed to carry out polymerization‐induced self‐assembly (PISA) and study the nanostructure behaviors.

One-For-All Polyolefin Functionalization: Active Ester as Gateway to Combine Insertion Polymerization with ROP, NMP, and RAFT.

This work develops the Polyolefin Active-Ester Exchange (PACE) process to afford well-defined polyolefin-polyvinyl block copolymers. α-Diimine PdII -catalyzed olefin polymerizations were investigated through in-depth kinetic studies in comparison to an analog to establish the critical design that facilitates catalyst activation. Simple transformations lead to a diversity of functional groups forming polyolefin macroinitiators or macro-mediators for various subsequent controlled polymerization techniques. Preparation of block copolymers with different architectures, molecular weights, and compositions was demonstrated with ring-opening polymerization (ROP), nitroxide-mediated polymerization (NMP), and photoiniferter reversible addition-fragmentation chain transfer (PI-RAFT). The significant difference in the properties of polyolefin-polyacrylamide block copolymers was harnessed to carry out polymerization-induced self-assembly (PISA) and study the nanostructure behaviors.

Synthesis of High-Molecular-Weight Branched Polyethylene Using a Hybrid "Sandwich" Pyridine-Imine Ni(II) Catalyst.

Most pyridine-imine Ni(II) and Pd(II) catalysts tend to yield low-molecular-weight polyethylene and ethylene-based copolymers in olefin insertion polymerization, as the unilateral axial steric structure of such complexes often cannot provide effective shielding of the metal center. In this study, we synthesized a series of hybrid “semi-sandwich” and “sandwich” type pyridine-imine Ni(II) complexes by incorporating diarylmethyl or dibenzosuberyl groups onto 8-aryl-naphthyl motif. The as-prepared Ni(II) complexes afforded highly branched polyethylene with high molecular weights (level of 105 g/mol), and moderate activities (level of 105 g/(molh)) in ethylene polymerization. Most interestingly, compared to “semi-sandwich” Ni(II) complexes bearing (2-diarylmethyl-8-aryl)naphthyl units, the “full-sandwich” counterpart containing (2-dibenzosuberyl-8-aryl)naphthyl motif was able to produce higher-molecular-weight polyethylene with higher branching density. In addition, the effect of remote non-conjugated electronic substituents in diarylmethyl groups of the Ni(II) system was also observed in ethylene polymerization.

Tunable “In-Chain” and “At the End of the Branches” Methyl Acrylate Incorporation in the Polyolefin Skeleton through Pd(II) Catalysis

The synthesis of functionalized polyolefins through coordination–insertion polymerization is a highly challenging reaction. The ideal catalyst, in addition to showing a high productivity, has to be able to control the copolymer microstructure and, in particular, the way of the polar vinyl monomer incorporation. In this contribution, we modified the typical Brookhart’s catalyst by introducing in the fourth coordination site of palladium a hemilabile, potentially bidentate ligand, such as a thiophenimine (N–S). The obtained cationic Pd(II) complexes, [Pd(Me)(N–N)(N–S)][PF6], generated active catalysts for the ethylene/methyl acrylate (MA) copolymerization leading to the desired copolymer with a different incorporation of the polar monomer depending on both the reaction medium and the N–S ligand. Surprisingly enough, the produced copolymers have the inserted acrylate both at the end of the branches (T(MA)) and in the main chain (M(MA)) in a ratio M(MA)/T(MA) that goes from 9:91 to 45:55 moving from dichloromethane to trifluoroethanol (TFE) as a solvent for the catalysis and varying the N–S ligand. The catalytic behavior of the new complexes was compared to that of the parent compound [Pd(Me)(N–N)(MeCN)][PF6], highlighting the fact that when the copolymerization is carried out in trifluoroethanol, this complex is also able to produce the E/MA copolymer with MA inserted both in the main chain and at the end of the branches. Accurate NMR studies on the reactivity of the precatalyst [Pd(Me)(N–N)(MeCN)][PF6] with the two comonomers allowed us to discover that in the fluorinated solvent, the catalyst resting state is an open-chain intermediate having both the organic fragment, originated from the migratory insertion of MA into the Pd–Me bond, and the acetonitrile coordinated to palladium and not the six-membered palladacycle typically observed for the Pd-α-diimine catalysts. This discovery is also supported by both DFT calculations and in situ NMR studies carried out on [Pd(Me)(N–N)(N–S)][PF6] complexes that point out that N–S remains in the palladium coordination sphere during catalysis. The open-chain intermediate is responsible for the growth of the copolymer chain with the polar monomer inserted into the main chain.

Second coordination sphere effect of benzothiophene substituents on chain transfer and chain walking in ethylene insertion polymerization

Recently, the α-diimine Ni(II) and Pd(II) catalysts bearing various diarylmethyl substituents on the N-aryl group have drawn much attention. In this work, two bulky diarylmethyl α-diimine Ni(II) catalysts bearing naphthyl and benzothiophene groups were synthesized and employed in ethylene polymerization. The Ni(II) complex bearing naphthyl groups exhibited high activities (ca. 106 g mol−1 h−1) and yielded highly branched (60–70/1000C) polyethylenes with high molecular weights (Mn up to 784.5 kg/mol) in ethylene polymerization. Moreover, this complex exhibited excellent thermal stability at high temperatures, and the polyethylene products obtained demonstrated good mechanical properties (SR up to 59%). Meanwhile, the Ni(II) complex bearing benzothiophene groups displayed high activities (ca. 106 g mol−1 h−1), and generated lightly branched (15–37/1000C) polyethylene with particularly high molecular weights (Mn up to 2017.6 kg/mol) at low temperatures. At high temperatures, the polymerization activity and the molecular weight of the obtained polyethylene decreased significantly. The second coordination sphere effect of benzothiophene substituents is considered to be responsible for the above experimental results.

The effect of CX (alkyl groups) on the migration insertion polymerization (MIP) of PFpCX [PFp = (PPh2(CH2)3Cp)Fe(CO)2

Migration insertion polymerization (MIP) of organometallic monomers, PFpCX [PFp = (PPh2(CH2)3Cp)Fe(CO)2, CX = (CH2)X-1CH3, X = 12 or 18] was performed under various conditions. The oligomerization occurred in accompany with the monomer cyclization generating PFpCX small rings at the early stage, which was followed by a complete cyclization of the oligomers generating P(PFpCX)n macrocycles. PFpCX small rings could be completely removed via precipitating the crude products in a poor solvent for the macrocycles. The solution and bulk MIP of PFpCX (X = 12 or 18) had a similar cyclization rate but both were significantly accelerated at a higher MIP temperature (100 °C). It is explained by the temperature-dependent tendency for the cyclization. The dependence of degree of polymerization (DP) on the MIP conditions was discussed and the self-assembly of resultant P(PFpC12)n was examined.

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Migration insertion polymerization (MIP) of organometallic monomers, PFpCX [PFp = (PPh2(CH2)3Cp)Fe(CO)2, CX = (CH2)X-1CH3, X = 12 or 18] was performed under various conditions. The oligomerization occurred in accompany with the monomer cyclization generating PFpCX small rings at the early stage, which was followed by a complete cyclization of the oligomers generating P(PFpCX)n macrocycles. PFpCX small rings could be completely removed via precipitating the crude products in a poor solvent for the macrocycles. The solution and bulk MIP of PFpCX (X = 12 or 18) had a similar cyclization rate but both were significantly accelerated at a higher MIP temperature (100 °C). It is explained by the temperature-dependent tendency for the cyclization. The dependence of degree of polymerization (DP) on the MIP conditions was discussed and the self-assembly of resultant P(PFpC12)n was examined.

Copper‐Catalyzed Si—H Bond Insertion Polymerization for Synthesis of Optically Active Polyesters Containing Silicon

Comprehensive SummaryThe synthesis and characterization of chiral polymers with diverse structure remain a long‐term challenging research topic. Herein, a copper‐catalyzed enantioselective insertion of carbene into Si—H bond was applied to polycondensation, giving a new type of optically active degradable polyesters containing Si—C bond in the main chain. The polymerization features mild condition, broad substrate scope, excellent yields and enantioselectivities. Chiral diols could be obtained via reduction of optically active polyesters. Thermogravimetric analysis indicated these chiral polyesters exhibit good thermal stability.

Cis-1,4 Selective Coordination Polymerization of 1,3-Butadiene and Copolymerization with Polar 2-(4-Methoxyphenyl)-1,3-butadiene by Acenaphthene-Based α-Diimine Cobalt Complexes Featuring Intra-Ligand π-π Stacking Interactions.

Highly cis-1,4 selective (up to 98%) coordination–insertion polymerization of 1,3-butadiene (BD) has been achieved herein using acenaphthene-based α-diimine cobalt complexes. Due to the presence of intra-ligand π-π stacking interactions, the complexes revealed high thermostability, affording polybutadiene products in high yields. Moreover, all of the obtained polymers possessed a relatively narrow molecular weight distribution as well as high molecular weight (up to 92.2 × 104 Dalton). The molecular weights of the resultant polybutadienes could be finely tuned by varying polymerization parameters, including temperature, Al/Co ratio, etc. Moreover, the copolymerization of butadiene with polar monomer 2-(4-methoxyphenyl)-1,3-butadiene (2-MOPB) was also successfully realized to produce a type of polar cis-1,4 polybutadiene (cis-1,4 content: up to 98.1%) with a range of 2-MOPB content (0.46–1.83%). Water contact angle measurements indicated that the insertion of a polar monomer into a polymer chain could significantly improve the polymer’s surface property.

Facile Access to Polar-Functionalized Ultrahigh Molecular Weight Polyethylene at Ambient Conditions

Facile Access to Polar-Functionalized Ultrahigh Molecular Weight Polyethylene at Ambient Conditions