Self-Consistent Theory for Structural Relaxation, Dynamic Bond Exchange Times, and the Glass Transition in Polymeric Vitrimers

Macromolecules, Год журнала: 2024, Номер 57(7), С. 3242 - 3257

Опубликована: Март 28, 2024

We formulate a statistical mechanical theory for how dynamic bond exchange influences the activated hopping-driven relaxation of Kuhn segments in dynamically cross-linked networks or vitrimers over wide range temperatures and cross-link densities. The key new methodological aspect is to address self-consistent manner consequences on segmental alpha relaxation, vice versa. predicted temperature dependence time at high remains same as that permanent networks, but lower temperatures, significant acceleration occurs due exchanges. From mechanistic perspective, vitrimer local cage barrier very weakly affected by exchange, while collective elastic contribution decreases significantly deeply supercooled regime. glass transition grow linearly with square root density, previously found networks. Material-specific chemical effects such cross-linker size relative normal segment special attraction polymers are crudely considered based model calculations. quantitatively applied recent experiments dry ethylene vitrimers. Good agreements including follows an Arrhenius law enough upward non-Arrhenius deviations emerge regime, collapsed master curve exists densities temperatures. Possible extensions treat heterogeneity penetrant transport briefly discussed.

Язык: Английский

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Dynamic Covalent Bond-Based Polymer Chains Operating Reversibly with Temperature Changes

Molecules, Год журнала: 2024, Номер 29(14), С. 3261 - 3261

Опубликована: Июль 10, 2024

Dynamic bonds can facilitate reversible formation and dissociation of connections in response to external stimuli, endowing materials with shape memory self-healing capabilities. Temperature is an stimulus that be easily controlled through heat. covalent temperature reversibly connect, exchange, convert chains the polymer. In this review, we introduce dynamic operate without catalysts various ranges. The basic bonding mechanism kinetics are examined understand chemistry performed by equilibrium control. Furthermore, a recent synthesis method implements coupling based on polymers introduced. depending applied expand use polymers, providing predictions for development future smart materials.

Язык: Английский

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Thermoswitchable catalysis to inhibit and promote plastic flow in vitrimers

Chemical Science, Год журнала: 2024, Номер 15(19), С. 7061 - 7071

Опубликована: Янв. 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.

Язык: Английский

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Molecular Dynamics Simulation and Theoretical Analysis of Structural Relaxation, Bond Exchange Dynamics, and Glass Transition in Vitrimers

Macromolecules, Год журнала: 2025, Номер unknown

Опубликована: Янв. 30, 2025

Язык: Английский

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Phase separation in supramolecular and covalent adaptable networks

Soft Matter, Год журнала: 2023, Номер 19(16), С. 2857 - 2877

Опубликована: Янв. 1, 2023

In this review we highlight the underlying mechanisms of phase separation in dynamic polymer networks, distinguishing between supramolecular networks and covalent adaptable discuss effect on material properties.

Язык: Английский

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Enhancing the Equilibrium of Dynamic Thia-Michael Reactions through Heterocyclic Design

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(26), С. 14427 - 14434

Опубликована: Июнь 23, 2023

Although the catalyst-free dynamic thia-Michael (tM) reaction has been leveraged for a range of significant applications in materials science and pharmaceutical development, exploiting its full potential limited by relatively low equilibrium constants. To address this shortcoming, new series catalyst-free, room-temperature acceptors bearing an isoxazolone motif were developed utilized to access both covalent networks linear polymers. By leveraging generation aromaticity upon thiol addition tuning electronic-withdrawing/donating nature acceptor at two different sites, wide constants (Keq ∼1000 ∼100,000 M-1) obtained, constituting 2 orders magnitude increase compared their noncyclic benzalcyanoacetate analogues. Integration into ditopic isoxazolone-based Michael allowed bulk polymers; these not only exhibited tailorable thermomechanical properties based on composition, but higher Keq tM bonds resulted more mechanically robust relative past designs. Furthermore, solution-state formation polymers was achieved thanks increased acceptors.

Язык: Английский

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Next‐Generation Vitrimers Design through Theoretical Understanding and Computational Simulations

Advanced Science, Год журнала: 2023, Номер 11(5)

Опубликована: Дек. 7, 2023

Abstract Vitrimers are an innovative class of polymers that boast a remarkable fusion mechanical and dynamic features, complemented by the added benefit end‐of‐life recyclability. This extraordinary blend properties makes them highly attractive for variety applications, such as automotive sector, soft robotics, aerospace industry. At their core, vitrimer materials consist crosslinked covalent networks have ability to dynamically reorganize in response external factors, including temperature changes, pressure variations, or shifts pH levels. In this review, aim is delve into latest advancements theoretical understanding computational design vitrimers. The review begins offering overview fundamental principles underlie behavior these materials, encompassing structures, behavior, reaction mechanisms. Subsequently, recent progress vitrimers explored, with focus on employment molecular dynamics (MD)/Monte Carlo (MC) simulations density functional theory (DFT) calculations. Last, existing challenges prospective directions field critically analyzed, emphasizing necessity additional advancements, coupled experimental validation.

Язык: Английский

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Green Catalysts for Reprocessing Thermoset Polyurethanes

Macromolecules, Год журнала: 2023, Номер 56(17), С. 6978 - 6987

Опубликована: Авг. 27, 2023

Polyurethane (PU) thermosets are usually landfilled at the end of their service lifetimes and cannot be recycled through conventional means. Although dibutyltin dilaurate (DBTDL) is an effective catalyst for reprocessing PU thermosets, organotins immunotoxic teratogenic, which concerning catalysts embedded within covalent adaptable networks (CANs). Here, we identify Zr(acac)4 Zr(tmhd)4 as to reprocess CANs more sustainably. Thermoset foams containing Zr-based exhibit characteristic stress relaxation times between 6 200 s, similar or faster than DBTDL. These capable a foam four five cycles. Dynamic mechanical thermal analysis indicates that zirconium-based preserve glass transition temperature crosslink density cycles promising bulk thermoset PUs. Furthermore, solvent-free method was developed by co-milling Zr catalyst. Ultimately, these methods using will impart greater sustainability circularity plastics.

Язык: Английский

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Mechanically Interlocked Vitrimer Based on Polybenzoxazine and Polyrotaxane

ACS Applied Polymer Materials, Год журнала: 2023, Номер 5(6), С. 3971 - 3978

Опубликована: Май 8, 2023

A mechanically interlocked vitrimer (MIV) based on a benzoxazine monomer and polyrotaxane (PR) has been prepared through network (MIN) dynamic covalent bond chemistry. The transacetalation exchange the N,O-acetal-type polybenzoxazine (PBz) structure was catalyzed by tin compound. Compared to controlled PBz without MIN, designed MIV shows enhanced mechanical performance including ductility tensile strength while maintaining relatively high Young's modulus glass transition temperature (Tg). can be reprocessed several times compromising thermal stability. also exhibits faster lower activation energy compared due mobile intramolecular motions of PR in allowing for more readily. usefulness present study preparation high-performance eco-friendly thermosetting vitrimers is discussed.

Язык: Английский

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A mechanically Robust, Damping, and High‐Temperature Tolerant Ion‐Conductive Elastomer for Noise‐Free Flexible Electronics

Advanced Functional Materials, Год журнала: 2024, Номер 34(46)

Опубликована: Июль 18, 2024

Abstract Ion‐conductive elastomers capable of damping can significantly mitigate the interference caused by mechanical noise during data acquisition in wearable and biomedical devices. However, currently available often lack robust properties have a narrow temperature range for effective damping. Here, precise modulation weak to strong ion‐dipole interactions plays crucial role bolstering network stability tuning relaxation behavior supramolecular ion‐conductive (SICEs). The SICEs exhibit impressive properties, including modulus 13.2 MPa, toughness 65.6 MJ m −3 , fracture energy 74.9 kJ −2 . Additionally, they demonstrate remarkable capabilities, with capacity 91.2% peak tan δ 1.11. Furthermore, entropy‐driven rearrangement ensures SICE remain stable even at elevated temperatures (18–200 °C, > 0.3), making it most thermally resistant elastomer reported date. Moreover, proves filtering out various noises physiological signal detection strain sensing, highlighting its vast potential flexible electronics.

Язык: Английский

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