Masked Primary Amines for a Controlled Plastic Flow of Vitrimers

ACS Macro Letters, Journal Year: 2022, Volume and Issue: 11(7), P. 919 - 924

Published: July 6, 2022

We present a simple method for increasing the reprocessability of vinylogous urethane (VU) vitrimers while decreasing possibility creep deformation at lower temperatures. In particular, varying amounts triethylenetetramine were added as comonomer to curing VU formulation ensure that all primary amines reacted form enaminone cross-links, resulting in network without reactive amine chain-ends. As result, transamination was significantly slowed down because secondary are much less exchange. On other hand, higher temperatures, pendent can be released via dynamic, endothermic exchange with nearby less-reactive amine, thereby (re)activating material flow. ambivalent viscoelastic behavior could achieved depolymerization by dynamically releasing from polymer chains. Through careful selection, low viscosity processing temperatures and same time high service prepared use catalysts or additives, leveraging synergistic effects mildly functionalities through neighboring group participation.

Language: Английский

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Recyclable high-performance glass-fiber/epoxy composites with UV-shielding and intrinsic damage self-reporting properties

Chemical Engineering Journal, Journal Year: 2022, Volume and Issue: 446, P. 137392 - 137392

Published: June 6, 2022

Language: Английский

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In-situ forming dynamic covalently crosslinked nanofibers with one-pot closed-loop recyclability

Nature Communications, Journal Year: 2023, Volume and Issue: 14(1)

Published: March 2, 2023

Polymeric nanofibers are attractive nanomaterials owing to their high surface-area-to-volume ratio and superior flexibility. However, a difficult choice between durability recyclability continues hamper efforts design new polymeric nanofibers. Herein, we integrate the concept of covalent adaptable networks (CANs) produce class ⎯ referred dynamic covalently crosslinked (DCCNFs) via electrospinning systems with viscosity modulation in-situ crosslinking. The developed DCCNFs possess homogeneous morphology, flexibility, mechanical robustness, creep resistance, as well good thermal solvent stability. Moreover, solve inevitable issues performance degradation crack nanofibrous membranes, DCCNF membranes can be one-pot closed-loop recycled or welded through thermal-reversible Diels-Alder reaction. This study may unlock strategies fabricate next generation recyclable features consistently chemistry for intelligent sustainable applications.

Language: Английский

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Direct and Catalyst-Free Ester Metathesis Reaction for Covalent Adaptable Networks

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(38), P. 20927 - 20935

Published: Sept. 15, 2023

Thermosetting polymers possess excellent environmental resistance and mechanical properties but cannot be reprocessed due to their covalently cross-linked structures. Recycling of thermosets via the implantation dynamic covalent bonds offers a promising solution. Here, we report direct catalyst-free ester metathesis N-acyloxyphthalimide (NAPI) at about 100 °C without requirement hydroxyl groups its utilization for fabrication adaptable networks (CANs). NAPI has interesting sigmoid kinetics with fast exchange rate, which proceeds free radical chain mechanism, guaranteeing associative under rather low dissociation. The bifunctional molecule as both precursor substrate is key dissociatively initiated (DAssociative) mechanism kinetic behavior. Based on efficient metathesis, polyester networks, poly(N-acyloxyphthalimides) (PNAPIs), show malleability. Notably, PNAPIs exhibit exceptional solvent stability elevated temperatures owing unique DAssociative suggesting exciting opportunities designing recyclable thermosetting polymers.

Language: Английский

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Covalent Adaptable Networks Made by Reactive Processing of Highly Entangled Polymer: Synthesis-Structure-Thermomechanical Property-Reprocessing Relationship in Covalent Adaptable Networks

Macromolecules, Journal Year: 2024, Volume and Issue: 57(6), P. 2756 - 2772

Published: March 6, 2024

Reactive processing provides a simple approach for grafting dynamic covalent cross-linkers onto linear or branched polymers, resulting in adaptable networks (CANs). We synthesized poly(n-hexyl methacrylate) (PHMA) CANs from neat, entangled PHMA using radical-based reactive to graft the cross-linker called BiTEMPS methacrylate (BTMA) between side chains. By tuning BTMA loading, we achieved range of cross-link densities and characterized how stress relaxation, elevated-temperature creep, reprocessability are affected by density. The cross-links chains allowed novel comparison our reversible, polymers described sticky reptation theory, which long-time relaxation occurs unraveling backbone entanglements, process enabled dissociation subsequent exchange side-chain "stickers." observed two regimes that required their fitting combination stretched exponential decay functions extract pertinent parameters. apparent activation energies creep viscosity same within experimental uncertainty these CANs, verifying shared mechanisms governing temperature dependence viscoelastic responses, independent CAN Notably, made linking ∼50–60% those reported previously with chain backbones. These outcomes demonstrate importance synthesis-structure-property-reprocessing relationships may be various methods varying position incorporation structure.

Language: Английский

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Deciphering the Self-Catalytic Mechanisms of Polymerization and Transesterification in Polybenzoxazine Vitrimers

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(19), P. 13367 - 13376

Published: May 2, 2024

The use of internal catalysts has emerged as a pivotal design principle to facilitate dynamic exchanges within covalent adaptable networks (CANs). Polybenzoxazines, specifically, have shown considerable potential in generating vitrimers through thermally induced transesterification reactions catalyzed internally by tertiary amines. This study aims investigate the chemical complexities benzoxazine vitrimers. To achieve this, model molecules using various phenolic acids and amino-alcohol derivatives were synthesized precursors. structure these was fully elucidated nuclear magnetic resonance (NMR). Differential scanning calorimetry (DSC) rheology experiments evidenced accelerated network formation precursors due presence aliphatic −OH groups. Thermogravimetric analysis coupled with microcomputed gas chromatography (TGA-μGC) used provide evidence reactions. results showed that spatial proximity between amine hydroxyl groups significantly enhances rate exchange, attributed neighboring group participation (NGP) effect. Interestingly, kinetic complementary NMR techniques revealed thermal latency toward its opening is needed trigger exchange. highlights crucial role steric hindrance basicity promoting exchange an system.

Language: Английский

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Enzyme-Initiated Devulcanization of Silicone–Gelatin Elastomers

ACS Sustainable Chemistry & Engineering, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 22, 2025

Language: Английский

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Room-Temperature Self-Healable and Mechanically Robust Thermoset Polymers for Healing Delamination and Recycling Carbon Fibers

ACS Applied Materials & Interfaces, Journal Year: 2021, Volume and Issue: 13(44), P. 53099 - 53110

Published: Oct. 27, 2021

The advocacy of carbon neutrality and circular economy encourages people to pursue self-healing recycling glassy thermoset polymers in a more realistic energy-saving manner, the best being intrinsic healing under room temperature. However, high mechanical robustness ability are mutually exclusive because their completely opposite requirements for mobility polymer networks. Here, we report dual-cross-linked network by slightly coupling low-molecular-weight branched polyethylenimine with an ester-containing epoxy monomer nonstoichiometric proportion. highly mobile dense noncovalent hydrogen bonds at chain branches ends can not only complement (tensile strength 61.6 MPa, elastic modulus 1.6 GPa, toughness 19.2 MJ/m3) but also endow (Tg > 40 °C) (healing efficiency 84%) 20 °C. Moreover, resultant covalent adaptive makes stable temperatures solvents, yet it is readily dissolved ethylene glycol through internal catalyzed transesterification. application temperature delamination fiber was demonstrated as proof-of-concept.

Language: Английский

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Combining vinylogous urethane and β-amino ester chemistry for dynamic material design

Polymer Chemistry, Journal Year: 2022, Volume and Issue: 13(14), P. 2008 - 2018

Published: Jan. 1, 2022

This study describes covalent adaptable networks with enhanced processability and creep resistance by combining vinylogous urea/urethane β-amino ester based dynamic motifs.

Language: Английский

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Internal catalysis on the opposite side of the fence in non-isocyanate polyurethane covalent adaptable networks

European Polymer Journal, Journal Year: 2022, Volume and Issue: 168, P. 111100 - 111100

Published: March 1, 2022

Language: Английский

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