Thermoswitchable catalysis to inhibit and promote plastic flow in vitrimers

Chemical Science, Journal Year: 2024, Volume and Issue: 15(19), P. 7061 - 7071

Published: Jan. 1, 2024

Acid-base catalysis is a common strategy to induce covalent bond exchanges in dynamic polymer networks. Strong acids or strong bases can promote rapid network rearrangements, and are simultaneously preferred catalysts for chemical reactions where maximum efficiency at the lowest possible temperature aimed for. However, within context of networks, incorporation highly active negatively affect longer term application potential. Network dynamicity diminish through catalyst ageing quenching may prematurely activate exchanges, leading dimensional instability thus low creep resistance Herein, we present several examples explicitly explored weak (carboxylic acids) as using vinylogous urethanes (VU) well-understood protic acid catalysed vitrimer chemistry. Surprisingly, have found that sought-after long-term stability offered by does not necessarily bring lower activity high temperature. In fact, show remarkable thermoswitchable catalytic behaviour, going from an inactive hydrogen bonded state matrix protonated, with profound impact on reactivity rheology. Carboxylic different electronic steric environments clear trends their fine-tuning resulted most thermally responsive VU vitrimers studied date. Our findings point out choice design only poorly informed performance more traditional (in solvent), tailored holds great promise field vitrimers.

Language: Английский

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Harnessing Mechanochemistry for Direct Synthesis of Imine-Based Metal–Organic Frameworks

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: March 11, 2025

The growth of metal–organic frameworks (MOFs) is most frequently accessed by the direct assembly metal cations and multitopic ready-to-connect ligands under solvothermal conditions. However, such nonambient conditions are expected to impose a synthetic challenge incorporate degradable into MOFs. This explains why imine-based MOFs scarce as imine motif usually prone decompose through hydrolysis. work not only showcases mechanochemistry an ambient, sustainable, high-yield strategy for synthesizing variety but also achieves integration ligand synthesis MOF single tandem step. Thus, this provides straightforward access MOFs, subfamily historically challenging materials.

Language: Английский

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Creep resistance in doubly crosslinked dynamic covalent networks

Polymer Chemistry, Journal Year: 2024, Volume and Issue: 15(18), P. 1826 - 1832

Published: Jan. 1, 2024

This work demonstrates that incorporating Janus-faced supramolecular moieties in vinylogous urethane vitrimers improved dimensional stability while conserving the hallmark vitrimer property of reprocessability.

Language: Английский

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Covalent adaptable networks and thermosets of multi-block ethylene/1-octene copolymers made by free-radical processing: Effects of melt flow index and crystallinity on thermomechanical properties and reprocessability

European Polymer Journal, Journal Year: 2023, Volume and Issue: 202, P. 112661 - 112661

Published: Dec. 5, 2023

Language: Английский

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Hybrid Chemomechanical Yielding of Covalent Adaptable Networks for Toughening Ionic Semi-Crystalline Epoxy

International Journal of Applied Mechanics, Journal Year: 2024, Volume and Issue: 16(06)

Published: March 2, 2024

Covalent adaptable network (CAN) in thermoset epoxy shows good recyclability due to its bond exchange reactions (BERs), which result low mechanical strength and toughness. Many experimental studies on using the semi-crystalline structures ions with CAN have shown improve toughness of these epoxies. However, their toughening mechanisms coupling effects not been well understood. Herein, we propose an extended Maxwell model explore semi-crystallization process formation ion phases CANs, enables hybrid chemomechanical yielding. A constitutive stress–strain relationship is formulated characterize yielding behavior, where first stage originated from effect amorphous phases, second ions. The proposed models verified results, provide a fundamental approach understanding epoxy.

Language: Английский

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Structure-Property Relationships to Direct the Dynamic Properties of Acylsemicarbazide-Based Materials

Polymer Chemistry, Journal Year: 2024, Volume and Issue: unknown

Published: Dec. 4, 2024

Secondary interactions, such as hydrogen bonding or phase separation, can enhance the stability of dynamic covalent materials without compromising on desired properties. Here, we investigate combination multiple secondary interactions in based acylsemicarbazides (ASCs), with aim achieving tunable material The effects different ASC substituents and capabilities were investigated a small molecule study using combined experimental theoretical approach, revealed presence cooperative hydrogen-bonding 2 directions one derivatives. motifs subsequently incorporated into polymeric materials. Combining capable strong, polydimethylsiloxane backbone introduces structure-dependent, ordered nanophase separation thermo-mechanical properties reveal strong dependance structure exact nature bond. behavior bulk shows that bond exchange depends dissociation rate obtained from model compounds, well strength these Differences structures also cause differences creep resistance Interestingly, hydrogen-bonded clusters show highest resistance. Our results demonstrate tuning both by molecular design is important for controlling their thermal

Language: Английский

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Design of Isocyanate-Free Biobased Polyurea Vitrimers with Dynamic Hydrogen and Imine Bonds, Offering Ambient Self-Healing, Reprocessing, and Recycling Properties

Macromolecules, Journal Year: 2024, Volume and Issue: unknown

Published: Dec. 25, 2024

A series of vitrimers combining dynamic hydrogen and imine bonds was prepared by a reaction between amine-terminated nonisocyanate polyurea oligomers (NIPUrea), terephthalaldehyde, tris(2-aminoethyl)amine at various equivalent ratios. NIPUrea different molecular weights were using an environmentally friendly sustainable approach, implying transurethane polycondensation technology. The possessed cross-linking densities exhibited Tg values around 20 °C, as well thermal stabilities exceeding 300 °C. They displayed high tunable mechanical strength ductility, with Young's modulus from 1.7 to 26.4 MPa, breaking stress 7.9 12.9 MPa elongation break 147 517%. revealed good solvent resistance except in acidic THF/water solutions, which they underwent irreversible degradation solubilization. Most the materials excellent self-healing efficiency room temperature (93 107%) reprocessability recyclability after hot pressing.

Language: Английский

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Molecular tuneability of Imine-based covalent adaptable networks

Published: March 6, 2023

In this chapter, we demonstrate that fine-grained, quantitative control over macroscopic dynamic material properties can be achieved using the Hammett equation in tuneable covalent polyimine materials.Via established physical-organic principle, operating on molecular level, one fine-tune and by systematic variation of bond dynamics through selection appropriate substituent aromatic imine building blocks.Five tuneable, crosslinked network materials, derived from dianiline monomers with varying parameter (σ) were studied rheology, revealing a distinct correlation between σ value range corresponding properties.Firstly, linear kinetic activation energy (Ea) for exchange to value, enabled us tune Ea 16 85 kJ•mol -1 .Furthermore, creep resistance, crossover temperature rubbery viscous phase (Tcross) topology freezing transition (Tv), all showed strong, often linear, dependence monomer.These combined results first time how directly tuned designed -and therefore predictable-manner correlations based equation.Moreover, materials found strong elastic rubbers (G' > 1 MPa at room temperature) stable up 300 °C, as confirmed TGA.Lastly, nature not only recycling, but also intrinsic self-healing multiple cycles without loss need additives, such solvent, catalysts or addition external chemicals.

Language: Английский

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Covalent Adaptable Networks and Thermosets of Multi-block Ethylene/1-Octene Copolymers Made by Free-Radical Processing: Effects of Melt Flow Index and Crystallinity on Thermomechanical Properties and Reprocessability

SSRN Electronic Journal, Journal Year: 2023, Volume and Issue: unknown

Published: Jan. 1, 2023

Chain shuttling polymerization has facilitated the rapid development of olefin block copolymers (OBCs) such as ethylene/1-octene multi-block copolymers. The properties OBCs stem from various parameters average length, number blocks per chain, etc., which lead to complexity associated with establishing structure-property relationships between precursor and cross-linked OBCs. Additionally, permanent cross-linking sacrifices their recyclability, capable being reprocessed have seldom been reported. Here, permanently (OBCXs) dynamically OBCs, or OBC covalent adaptable networks (CANs), were synthesized by melt-state reactive processing neat crystallinities melt flow indices (MFIs). CANs are dialkylamino disulfide dynamic chemistry via grafting bis(2,2,6,6-tetramethyl-4-piperidyl methacrylate) disulfide, BiTEMPS methacrylate, cross-linkers onto backbone chains. Thermomechanical characterizations indicate that increasing crystallinity decreasing MFI in higher cross-link densities OBCXs CANs. Dynamically into also significantly improves elevated-temperature creep resistance. Stress relaxation results an increased time greater density. Distinct other chemistry, stress behaviors density show evident dependence on network viscoelasticities. In lower density, more strongly governs behaviors. Finally, exhibit full thermomechanical property recovery after reprocessing, whereas cannot be due irreversible cross-links.

Language: Английский

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