Transcarbamoylation in Polyurethanes: Underestimated Exchange Reactions?

Macromolecules, Journal Year: 2022, Volume and Issue: 55(18), P. 7974 - 7991

Published: Sept. 5, 2022

While transesterification has been largely explored by chemists, only a few studies comparatively dealt with its "sluggish cousin", transcarbamoylation. Originally suggested 70 years ago to explain the stress decay observed at high temperature in polyurethane chemical networks, transcarbamoylation─also called transurethanization or urethane exchange─is still underexploited both organic and polymer chemistry. This is mainly related use of toxic reactants such as isocyanates tin-based catalysts involved during preparation molecular carbamates polyurethanes (PUs) well harsh conditions required observe exchanges transformations. Many have focused their interest alternatives isocyanates, underestimating potential transcarbamoylation produce, recycle, reprocess PUs (wastes). Perspective presents latest developments plausible future directions prepare sustainable PU-based materials using focus on covalent dynamic networks.

Language: Английский

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Catalyst-Free Epoxy Vitrimers Based on Transesterification Internally Activated by an α–CF₃ Group

Macromolecules, Journal Year: 2022, Volume and Issue: 55(5), P. 1669 - 1679

Published: Feb. 21, 2022

Vitrimers are polymer networks in which associative exchange reactions can take place under specific conditions, thus conferring reprocessability to insoluble materials. Recently, catalyst-free vitrimers have emerged as a new generation of able overcome potential leaching, aging, and sintering issues catalysts ensure the preservation vitrimer properties after numerous reshaping processes. Here, epoxy featuring α-CF3-substituted ester functions is reported. First, tetra-acid precursor was synthesized via thia-Michael addition. A ring-opening polymerization then performed on two different diepoxy monomers (DGEBA BDGE) obtain composed linkages. Curing evaluated by rheology, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) monitoring kinetics. gel content over 70% measured 24 h tetrahydrofuran (THF). Finally, accelerating effect α-CF3 group transesterification highlighted stress-relaxation experiments analyzed computationally molecular model system. Reprocessability tests were carried out at 150 °C for 2 h. The mechanical thermal reshaped materials similar those initial ones. This study demonstrates fluorinated groups powerful internal activators vitrimers.

Language: Английский

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Strong, Supertough and Self‐Healing Biomimetic Layered Nanocomposites Enabled by Reversible Interfacial Polymer Chain Sliding

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(23)

Published: April 3, 2023

Despite the remarkable progress in ultrastrong mechanical laminate materials, simultaneous achievement of toughness, stretchability and self-healing properties biomimetic layered nanocomposites remains a great challenge due to intrinsic limitations their hard essences lack effective stress transfer at organic-inorganic fragile boundary. Here, an ultratough nanocomposite is prepared by constructing chain-sliding cross-linking interface between sulfonated graphene nanosheets polyurethane layers based on ring molecules sliding linear polymer chains release stresses. Unlike traditional supramolecular bonding toughening with limited spacing, our strategy enables interfacial molecular reversible slippage when inorganic bear stretching force, providing sufficient interlayer spatial distance for relative dissipate more energy. The resulting laminates exhibit strong strength (22.33 MPa), supertoughness (219.08 MJ m-3 ), ultrahigh (>1900 %) ability (99.7 %), which far surpass most reported synthetic natural materials. Moreover, fabricated proof-of-concept electronic skin shows excellent flexibility, sensitivity healability human physiological signals monitoring. This breaks through that are intrinsically stiff opens up functional application flexible devices.

Language: Английский

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On the Welding of Vitrimers: Chemistry, Mechanics and Applications

Advanced Functional Materials, Journal Year: 2023, Volume and Issue: 33(36)

Published: May 18, 2023

Abstract Linear chains in thermoplastics make them relatively weak performance but inherently weldable and recyclable. By contrast, thermosets with permanently crosslinked networks possess outstanding mechanical performance, thermal, chemical stability, are unweldable unrecyclable. In the last decade, a kind of thermoplastics‐like termed as vitrimer has been developed extensive applications, which welding vitrimers plays central fundamental role. Herein, we present current state art discuss from broad picture chemistry, physics, mechanics: i) chemistry mechanics vitrimers; ii) applicability assessment methods for iii) design principles implement strategies to iv) effects conditions on strength toughness; v) applications adhesion chemically inert materials. Finally, advantages, challenges, open questions highlighted, future opportunities mechanics, tough welding, artificial intelligence aided programming technology, standard, so discussed. The development would fuse disciplines transformative impact polymer industry.

Language: Английский

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Introducing Dynamic Bonds in Light‐based 3D Printing

Advanced Functional Materials, Journal Year: 2023, Volume and Issue: 34(20)

Published: April 23, 2023

Abstract Light‐based 3D printing has received significant attention due to several advantages including high speed and resolution. Along with the development of new technologies, material design is key for next generation light‐based printing. Conventional printable polymeric materials, also known as photopolymers or photoresins, often lead thermosets–polymer networks cross‐linked by permanent covalent bonds which bring limited adaptability restricted reprocessability. Dynamic that can reversibly break reform enable network rearrangement, thereby offering unprecedented properties materials such adaptability, self‐healing, recycling capabilities. Hence, introducing dynamic into a promising strategy further expand meet diverse application scenarios printed multi‐functional moreover more demanding sustainable nature‐inspired considerations (e.g., self‐healing). Herein, an overview recent advances in printing, aiming bridge these two research fields presented. Importantly, current challenges are analyzed perspectives developing their potential applications provided.

Language: Английский

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