Ultrahigh Molecular Weight Polymers Research Articles

Mechanochemically Promoted Functionalization of Postconsumer Poly(Methyl Methacrylate) and Poly(α-Methylstyrene) for Bulk Depolymerization.

We describe a methodology of post-polymerization functionalization to enable subsequent bulk depolymerization to monomer by utilizing mechanochemical macro-radical generation. By harnessing ultrasonic chain-scission in the presence of N-hydroxyphthalimide methacrylate (PhthMA), we successfully chain-end functionalize polymers to promote subsequent depolymerization in bulk, achieving up to 81% depolymerization of poly(methyl methacrylate) (PMMA) and poly(α-methylstyrene) (PAMS) within 30 min. This method of depolymerization yields a high-purity monomer that can be repolymerized. Moreover, as compared to the most common methods of depolymerization, this work is most efficient with ultra-high molecular weight (UHMW) polymers, establishing a method with the potential to address highly persistent, non-degradable all-carbon backbone plastic materials. Lastly, we demonstrate the expansion of this depolymerization method to commercial cell cast PMMA, achieving high degrees of depolymerization from post-consumer waste. This work is the first demonstration of applying PhthMA-promoted depolymerization strategies in homopolymer PMMA and PAMS prepared by conventional polymerization methods.

Synthesis of ultra-high molecular weight homo- and copolymers via an ultrasonic emulsion process with a fast rate

In the forefront of advanced materials, ultra-high molecular weight (UHMW) polymers, renowned for their outstanding mechanical properties, have found extensive applications across various domains. However, their production has encountered a significant challenge: the attainment of UHMW polymers with a low dispersity (Ɖ). Herein, we introduce the pioneering technique of ultrasound (US) initiated polymerization, which has garnered attention for its capability to successfully polymerize a multitude of monomers. This study showcases the synthesis of UHMW polymers with a comparatively low Ɖ ( ≤ 1.1) within a remarkably short duration ( ~ 15 min) through the amalgamation of emulsion polymerization and high-frequency ultrasound-initiated polymerization. Particularly noteworthy is the successful copolymerization of diverse monomers, surpassing the molecular weight and further narrowing the Ɖ compared to their respective homopolymers. Notably, this includes monomers like vinyl acetate, traditionally deemed unsuitable for controlled polymerization. The consistent production and uniform dispersion of radicals during ultrasonication have been identified as key factors facilitating the swift fabrication of UHMW polymers with exceptionally low Ɖ.

The synthesis of polymers with ultra‐high molecular weight by combining ROMP and acyclic metathesis reaction

AbstractRing opening metathesis polymerization (ROMP) is widely used to prepare functional materials with various topological structures. However, it is difficult to prepare polymers with ultra‐high molecular weight (UHMW) directly. We found a new method to prepare UHMW polymers by combining ROMP and acyclic metathesis reaction. First, monomer NB‐2OH was polymerized by ROMP with different feed ratio of NB‐2OH/G3, and obtained well‐defined polymers P(NB‐2OH)n (n = 50, 200, and 463). Then acyclic metathesis reaction was used to synthesize UHMW polymers. The results indicated that polymer P(NB‐2OH)z with higher molecular weight (Mw = 6067.3 kg mol−1) and narrower distribution (PDI = 1.58) could be obtained at 80°C for 5 min, when P(NB‐2OH)463 was used as raw material with H2SO4/G3 = 10/1. Compared with polymer P(NB‐2OH)1990 (Mw = 5343.1 kg mol−1, PDI = 1.61) prepared by ROMP directly, the new method tremendously shortens reaction time, lowers the requirement for the purity of monomer and produces UHMW polymers with narrower distribution. The compositions of prepared polymers were also confirmed clearly by post‐modification and 1H NMR characterization.

Enhancing mechanical properties of composite solid electrolyte by ultra-high molecular weight polymers

Composite solid electrolytes combining the advantages of inorganic and polymer electrolytes are considered as one of the promising candidates for solid-state lithium metal batteries. Compared with ceramic-in-polymer electrolyte, polymer-in-ceramic electrolyte displays excellent mechanical strength to inhibit lithium dendrite. However, polymer-in-ceramic electrolyte faces the challenges of lack of flexibility and severely blocked Li+ transport. In this study, we prepared polymer-in-ceramic film utilizing ultra-high molecular weight polymers and ceramic particles to combine flexibility and mechanical strength. Meanwhile, the ionic conductivity of polymer-in-ceramic electrolytes was improved by adding excess lithium salt in polymer matrix to form polymer-in-salt structure. The obtained film shows high stiffness (10.5 MPa), acceptable ionic conductivity (0.18 mS cm−1) and high flexibility. As a result, the corresponding lithium symmetric cell stably cycles over 800 h and the corresponding LiFePO4 cell provides a discharge capacity of 147.7 mAh g−1 at 0.1 C without obvious capacity decay after 145 cycles.

Diversification of Acrylamide Polymers via Direct Transamidation of Unactivated Tertiary Amides.

Postpolymerization modification offers a versatile strategy for synthesizing complex macromolecules, yet modifying acrylamide polymers like poly(N,N-dimethylacrylamide) (PDMA) is notoriously challenging due to the inherent stability and low reactivity of amide bonds. In this study, we unveil a novel approach for the direct transamidation of PDMA, leveraging recent advances in the transamidation of unactivated tertiary amide substrates. By exploiting photoiniferter polymerization, we extended this direct transamidation approach to ultrahigh-molecular-weight (UHMW) PDMA, showcasing the unprecedented postpolymerization modification of synthetic polymers exceeding 106 g/mol. We also designed acrylamide copolymers comprising both the moderately reactive N-methyl-N-phenyl tertiary amides, along with the less reactive, fully alkyl-substituted N,N-dimethyl amides inherent to PDMA. This disparate reactivity enabled a sequential, chemoselective transamidation by initially targeting the more reactive pendant aryl amides with less nucleophilic aromatic amines, and second, transamidating the untouched N,N-dimethyl amide moieties with more nucleophilic aliphatic amines, yielding a uniquely diversified acrylamide copolymer. This work not only broadens the scope of postpolymerization modification strategies by pioneering direct transamidation of unactivated amides but also provides a robust platform for the design of intricate macromolecules, particularly in the realm of UHMW polymers.

Synthesis of megadalton stereoregular ring-substituted poly(phenylacetylene)s by a rhodium(i) catalyst with a N-functionalized hemilabile phosphine ligand

The compound [Rh(nbd){κ2P,N-Ph2P(CH2)3NMe2}][BF4] efficiently catalyzes the polymerization of ring-substituted phenylacetylenes to give highly stereoregular megadalton and ultra-high molecular weight polymers with moderate dispersity.

Visible-light-induced ATRP under high-pressure: synthesis of ultra-high-molecular-weight polymers.

In this study, a high-pressure-assisted photoinduced atom transfer radical polymerization (p ≤ 250 MPa) enabled the synthesis of ultra-high-molecular-weight polymers (UHMWPs) of up to 9 350 000 and low/moderate dispersity (1.10 < Đ < 1.46) in a co-solvent system (water/DMSO), without reaction mixture deoxygenation.

Ultra-high molecular weight complex coacervates via polymerization-induced electrostatic self-assembly

Advances in reversible-deactivation radical polymerization (RDRP), particularly the recent renaissance of photoiniferter polymerization, have led to new methods to achieve ultra-high molecular weight polymers with high functional-group tolerance.

Integrating Hybrid Perovskite Nanocrystals into Metal-Organic Framework as Efficient S-Scheme Heterojunction Photocatalyst for Synergistically Boosting Controlled Radical Photopolymerization under 980 nm NIR Light.

S-scheme heterojunction photocatalyst MAPbI3@PCN-222 with light absorption extending to the NIR region is constructed by embedding organic-inorganic hybrid perovskite (MAPbI3) into porphyrinic Zr-MOF (PCN-222). Both in situ X-ray photoelectron spectroscopy, ultraviolet photoelectron spectral characterization, and photocatalytic polymerization experiment prove the formation of S-scheme heterojunction. MAPbI3@PCN-222 with a low dosage (90 ppm) displays an impressive photocatalytic ability for 980 nm light-mediated photoinduced electron/energy-transfer-reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization in air. The well-defined controllable-molecular weight polymers including block copolymers and ultrahigh-molecular weight polymers can be achieved with narrow distributions (Mw/Mn < 1.20) via rapid photopolymerization. The industrial application potential of the photocatalyst also has been proved by scale-up synthesis of polymers with low polydispersity under NIR light-induced photopolymerization in a large-volume reaction system (200 mL) with high monomer conversion up to 99%. The penetration photopolymerization through the 5 mm polytetrafluoroethylene plate and excellent photocontrollable behavior illustrate the existence of long-term photogenerated electron transfer of heterojunction and abundant free radicals in photopolymerization. The photocatalyst still retains high catalytic activity after 10 cycles of photopolymerization in air. It is revealed for the first time that the special PET-RAFT polymerization pathway is initiated by the aldehyde-bearing α-aminoalkyl radical derived from the oxidization of triethanolamine (TEOA) by the heterojunction photocatalyst. This research offers a new insight into understanding the NIR-light-activated PET-RAFT polymerization mechanism in the presence of TEOA.

Nanosheet-Assembled Zirconium-Porphyrin Frameworks Enabling Surface-Confined, Initiator-Free Photosynthesis of Ultrahigh Molecular Weight Polymers.

Metal-organic frameworks with well-organized low-dimensional architectures provide significant thermodynamic and/or kinetic benefits for diverse applications. We present here the controlled synthesis of a novel class of hierarchical zirconium-porphyrin frameworks (ZrPHPs) with nanosheet-assembled hexagonal prism morphology. The crystal growth behaviors and structural evolution of ZrPHPs in an additive-modulated solvothermal synthesis are examined, showing an "assembly-hydrolysis-reassembly" mechanism towards the formation of 2D nanosheets with ordered arrangement. Because of the highly-accessible active sites harvesting broadband photons, ZrPHPs serve as adaptable photocatalysts to regulate macromolecular synthesis under full-range visible light and natural sunlight. An initiator-free, oxygen-tolerant photopolymerization system is established, following a distinctive mechanism involving direct photo-induced electron transfer to dormant species and hole-mediated reversible deactivation. Specifically, ZrPHPs provide a surface-confined effect towards the propagating chains which inhibits their recombination termination, enabling the highly-efficient synthesis of ultrahigh molecular weight polymers (Mn >1,500,000) with relatively low dispersity (Đ≈1.5).

Nanosheet‐Assembled Zirconium‐Porphyrin Frameworks Enabling Surface‐Confined, Initiator‐Free Photosynthesis of Ultrahigh Molecular Weight Polymers

AbstractMetal–organic frameworks with well‐organized low‐dimensional architectures provide significant thermodynamic and/or kinetic benefits for diverse applications. We present here the controlled synthesis of a novel class of hierarchical zirconium‐porphyrin frameworks (ZrPHPs) with nanosheet‐assembled hexagonal prism morphology. The crystal growth behaviors and structural evolution of ZrPHPs in an additive‐modulated solvothermal synthesis are examined, showing an “assembly‐hydrolysis‐reassembly” mechanism towards the formation of 2D nanosheets with ordered arrangement. Because of the highly‐accessible active sites harvesting broadband photons, ZrPHPs serve as adaptable photocatalysts to regulate macromolecular synthesis under full‐range visible light and natural sunlight. An initiator‐free, oxygen‐tolerant photopolymerization system is established, following a distinctive mechanism involving direct photo‐induced electron transfer to dormant species and hole‐mediated reversible deactivation. Specifically, ZrPHPs provide a surface‐confined effect towards the propagating chains which inhibits their recombination termination, enabling the highly‐efficient synthesis of ultrahigh molecular weight polymers (Mn &gt;1,500,000) with relatively low dispersity (Đ≈1.5).

Inverse Miniemulsion Enables the Continuous-Flow Synthesis of Controlled Ultra-High Molecular Weight Polymers.

We report the controlled synthesis of ultra-high molecular weight (UHMW) polymers (Mn ≥ 106 g/mol) via continuous flow in a tubular reactor. At high monomer conversion, UHMW polymers in homogeneous batch polymerization exhibit high viscosities that pose challenges for employing continuous flow reactors. However, under heterogeneous inverse miniemulsion (IME) conditions, UHMW polymers can be produced within the dispersed phase, while the viscosity of the heterogeneous mixture remains approximately the same as the viscosity of the continuous phase. Conducting such IME polymerizations in flow results in a faster rate of polymerization compared to batch IME polymerizations while still providing excellent control over molecular weight up to 106 g/mol. Crucial emulsion parameters, such as particle size and stability under continuous flow conditions, were examined using dynamic light scattering. A range of poly(N,N-dimethylacrylamide) and poly(4-acryloylmorpholine) polymers with molecular weights of 104-106 g/mol (Đ ≤ 1.31) were produced by this method using water-soluble trithiocarbonates as photoiniferters.

P-Azaquinodimethane: A Versatile Quinoidal Moiety for Functional Materials Discovery.

ConspectusThe past 50 years of discovery in organic electronics have been driven in large part by the donor-acceptor design principle, wherein electron-rich and electron-poor units are assembled in conjugation with each other to produce small band gap materials. While the utility of this design strategy is undoubtable, it has been largely exhausted as a frontier of new avenues to produce and tune novel functional materials to meet the needs of the ever-increasing world of organic electronics applications. Its sister strategy of joining quinoidal and aromatic groups in conjugation has, by comparison, received much less attention, to a great extent due to the categorically poor stability of quinoidal conjugated motifs.In 2017 though, the p-azaquinodimethane (AQM) motif was first unveiled, which showed a remarkable level of stability despite being a close structural analogue to p-quinodimethane, a notably reactive compound. In contrast, dialkoxy AQM small molecules and polymers are stable even under harsh conditions and could thus be incorporated into conjugated polymers. When polymerized with aromatic subunits, these AQM-based polymers show notably reduced band gaps that follow reversed structure-property trends to some of their donor-acceptor polymer counterparts and yield organic field-effect transistor (OFET) hole mobilities above 5 cm2 V-1 s-1. Additionally, in an ongoing study, these AQM-based compounds are also showing promise as singlet fission (SF) active materials due to their mild diradicaloid character.An expanded world of AQMs was accessed through their ditriflate derivatives, which were first used to produce ionic AQMs (iAQMs) sporting two directly attached cationic groups that significantly affect the AQM motif's electronics, producing strongly electron-withdrawing quinoidal building blocks. Conjugated polyelectrolytes (CPEs) created with these iAQM building blocks exhibit optical band gaps stretching into the near-infrared I (NIR-I) region and showed exemplary behavior as photothermal therapy agents.In contrast to these stable AQM examples, the synthetic exploration of AQMs also produced examples of more typical diradicaloid reactivity but in forms that were controllable and produced intriguing and high-value products. With certain substitution patterns, AQMs were found to dimerize to form highly substituted [2.2]paracyclophanes in distinctly more appreciable yields than typical cyclophane formation reactions. Certain AQM ditriflates, when crystallized, undergo light-induced topochemical polymerization to form ultrahigh molecular weight (>106 Da) polymers that showed excellent performances as dielectric energy storage materials. These same AQM ditriflates could be used to produce the strongly electron-donating redox-active pentacyclic structure: pyrazino[2,3-b:5,6-b']diindolizine (PDIz). The PDIz motif allowed for the synthesis of exceedingly small band gap (0.7 eV) polymers with absorbances reaching all the way into the NIR-II region that were also found to produce strong photothermal effects. Both as stable quinoidal building blocks and through their controllable diradicaloid reactivity, AQMs have already proven to be versatile and effective as functional organic electronics materials.

Highly stretchable and self-healable polymer gels from physical entanglements of ultrahigh-molecular weight polymers.

Highly stretchable and self-healing polymer gels formed solely by physical entanglements of ultrahigh–molecular weight (UHMW) polymers were fabricated through a facile one-step process. Radical polymerization of vinyl monomers in ionic liquids under very low initiator concentration conditions produced UHMW polymers of more than 106 g/mol with nearly 100% yield, resulting in the formation of physically entangled transparent polymer gels. The UHMW gels showed excellent properties, such as high stretchability, high ionic conductivity, and recyclability. Furthermore, the UHMW gel exhibited room temperature self-healing ability without any external stimuli. The tensile experiments and molecular dynamics simulations indicate that the nonequilibrium state of the fractured surfaces and microscopic interactions between the polymer chains and solvents play a vital role in the self-healing ability. This study provides a physical approach for fabricating stretchable and self-healing polymer gels based on UHMW polymers.

An Atom-Economic Enzymatic Cascade Catalysis for High-Throughput RAFT Synthesis of Ultrahigh Molecular Weight Polymers.

High-throughput synthesis of well-defined, ultrahigh molecular weight (UHMW) polymers by green approaches is highly desirable but remains unexplored. We report the creation of an atom-economic enzymatic cascade catalysis, consisting of formate oxidase (FOx) and horseradish peroxidase (HRP), that enables high-throughput reversible addition-fragmentation chain transfer (RAFT) synthesis of UHMW polymers at volumes down to 50 μL. FOx transforms formic acid, a C1 substrate, and oxygen to CO2 and H2 O2 , respectively. CO2 can escape from solution while H2 O2 is harnessed in situ by HRP to generate radicals from acetylacetone for RAFT polymerization, leaving no waste accumulation in solution. Oxygen-tolerant RAFT polymerization using enzymatic cascade redox cycles was successfully performed in vials and 96-well plates to produce libraries of well-defined UHMW polymers, and represents the first example of high-throughput synthesis method of such materials at extremely low volumes.

An Atom‐Economic Enzymatic Cascade Catalysis for High‐Throughput RAFT Synthesis of Ultrahigh Molecular Weight Polymers

AbstractHigh‐throughput synthesis of well‐defined, ultrahigh molecular weight (UHMW) polymers by green approaches is highly desirable but remains unexplored. We report the creation of an atom‐economic enzymatic cascade catalysis, consisting of formate oxidase (FOx) and horseradish peroxidase (HRP), that enables high‐throughput reversible addition‐fragmentation chain transfer (RAFT) synthesis of UHMW polymers at volumes down to 50 μL. FOx transforms formic acid, a C1substrate, and oxygen to CO2and H2O2, respectively. CO2can escape from solution while H2O2is harnessed in situ by HRP to generate radicals from acetylacetone for RAFT polymerization, leaving no waste accumulation in solution. Oxygen‐tolerant RAFT polymerization using enzymatic cascade redox cycles was successfully performed in vials and 96‐well plates to produce libraries of well‐defined UHMW polymers, and represents the first example of high‐throughput synthesis method of such materials at extremely low volumes.

Binary Hybridization Strategy toward Stable Porphyrinic Zr‐MOF Encapsulated Perovskites as High‐Performance Heterogeneous Photocatalysts for Red to NIR Light‐Induced PET‐RAFT Polymerization

AbstractStable binary nanohybrids based on all‐inorganic halide perovskite encapsulated in porphyrinic Zr‐MOF (PCN‐222) are constructed for photoinduced electron transfer‐reversible addition‐fragmentation chain transfer (PET‐RAFT) polymerization. The synergistic effect of perovskite and PCN‐222 endows the photocatalyst with high‐efficiency photogenic charge carrier separation and light absorption property. CsPbI3@PCN‐222 (20%) is finally screened out as the oxygen and solvent‐resistant photocatalyst for highly efficient photo‐controlled polymerization of conjugated and unconjugated monomers under red to near infrared (NIR) light with high monomer conversion and narrow molecular weight distribution well‐defined polymers (Đ &lt; 1.20). Controllable polymers and ultrahigh molecular weight polymers (up to 1730000 g mol−1) are successfully obtained by chain extension and block copolymerization of various monomers. The constructed photocatalysts easily achieve excellent light and temporal control, and even show high MMA conversion with NIR light under a thick barrier.

Synthesis of Ultra-High molecular weight polyethylene elastomers by para-tert-Butyl dibenzhydryl functionalized α-Diimine nickel catalysts at elevated temperature

The synthesis of polyethylene thermoplastic elastomers directly from ethylene as a feedstock is highly attractive in perception of their diverse applications and low cost. In this contribution, α-diimine nickel catalysts (Ni1-Ni4) with sterically bulky para-t-Bu dibenzhydryl moieties at ortho-position as well as different electron-donating and -withdrawing groups at para-position have been synthesized, characterized and applied for ethylene polymerization. These catalysts were found to be highly active with maximum activity up to 7.04 × 106 g·mol−1·h−1, producing polyethylene with ultra-high molecular weight of up to 333.4 × 104 g·mol−1. More remarkably, these catalysts have thermal stability of up to 140 °C. The t-Bu rich nature enables their good solubility in non-polar aliphatic hydrocarbons, which are industrially desired polymerization solvents. Furthermore, these catalysts generate polyethylene thermoplastic elastomers especially at industrially high temperature of 140 °C, with great mechanical properties and strain recover (SR) values of up to 75 %. The properties including high thermal stability, polymerization in aliphatic hydrocarbons, and capabilities of yielding elastic ultra-high molecular weight polymers make them highly attractive for potential industrial applications.

A Perspective on the History and Current Opportunities of Aqueous RAFT Polymerization.

Reversible addition-fragmentation chain transfer (RAFT) polymerization has proven itself as a powerful polymerization technique affording facile control of molecular weight, molecular weight distribution, architecture, and chain end groups - while maintaining a high level of tolerance for solvent and monomer functional groups. RAFT is highly suited to water as a polymerization solvent, with aqueous RAFT now utilized for applications such as controlled synthesis of ultra-high molecular weight polymers, polymerization induced self-assembly, and biocompatible polymerizations, among others. Water as a solvent represents a non-toxic, cheap, and environmentally friendly alternative to organic solvents traditionally utilized for polymerizations. This, coupled with the benefits of RAFT polymerization, makes for a powerful combination in polymer science. This perspective provides a historical account of the initial developments of aqueous RAFT polymerization at the University of Southern Mississippi from the McCormick Research Group, details practical considerations for conducting aqueous RAFT polymerizations, and highlights some of the recent advances aqueous RAFT polymerization can provide. Finally, some of the future opportunities that this versatile polymerization technique in an aqueous environment can offer are discussed, and it is anticipated that the aqueous RAFT polymerization field will continue to realize these, and other exciting opportunities into the future.

The rheology of ultra-high molecular weight poly(ethylene oxide) dispersed in a low molecular weight carrier.

Gel spinning is the industrial method of choice for combining hydrophilic ultra-high molecular weight (UHMW) polymer resins with a hydrophobic support polymer to produce composite filaments for cytapheresis. Cytapheresis is a medical technique for removal of leukocytes from blood. Gel spinning is used to avoid high melt viscosity and thermal sensitivity of UHMW resins and the high melt temperature of the substrate resin but requires the recovery of toxic solvents. The UHMW resin is used because it forms a stable gel phase in the presence of water; a lower molecular weight resin (LMW) simply dissolves. UHMW and LMW resins were both poly(ethylene oxide) (PEO) and the substrate was polyarylsulfone (PAS). The literature indicated PEO undergoes non-oxidative thermal degradation above 200 °C and PAS is processed up to 350 °C. Dynamic oscillatory shear rheometry was used to study 0, 25, 40, 50, 60, and 75 wt. % UHMW PEO in LMW PEO to take advantage of the sensitivity of viscosity to changes in molecular weight and material configuration, indicating degradation. Samples were exposed to 220 °C, 230 °C, 240 °C, 250 °C, 275 °C, and 300 °C temperatures for 5 min to explore conditions that could result in sample degradation. The viscosity decreased less with increasing UHMW PEO content for samples exposed to the same temperature and the viscosity decreased more with increasing exposure temperature for samples with the same UHMW PEO content. Parameters were regressed from observed data to predict the change in molecular weight via empiricisms relating the viscosity to molecular weight, shear rate, temperature, and time.