The crucial role of external force in the estimation of the topology freezing transition temperature of vitrimers by elongational creep measurements

Kaiser, Simon; Novak, Patrick; Giebler, Michael; Gschwandl, Mario; Novak, Philipp; Pilz, Gerald; Morak, Matthias; Schlögl, Sandra

doi:10.1016/j.polymer.2020.122804

Cited by 49 publications

(64 citation statements)

References 25 publications

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“…This value effectively represents the onset of a rearrangement that is exclusively dependent on the chemistry of the system (equivalently, independent of the applied external load). Above this value, in the case of the softer epoxy/acids networks, the effect of the entropy-driven elastic recoil superimposes creep, thus shifting T v again toward higher temperatures [49]. The shifting of T v is less pronounced in the case of stiffer epoxy/anhydride networks.…”

Section: Vitrimersmentioning

confidence: 93%

“…The latter hinges on a dimensional change as a result of activated exchange reactions in the proximity of T v [14]; the former allows detecting a change in the fluorescence of luminogens-doped vitrimers [48]. Kaiser et al reported a discrepancy between dilatometry and stress-relaxation, also as a consequence of the strong dependence of T v on the applied stress and the heat rate [49]. They carried out elongational creep measurements by applying a series of stress values (10 kPa-200 kPa) and heat rates on different well-known catalysed epoxy/anhydride and epoxy/acids systems.…”

Section: Vitrimersmentioning

confidence: 99%

“…They proved that low stress values lead to drawing deceptive conclusions on the actual kinetics of the system. In other words, as the applied stress increases, the T v of the system settles to a minimum, which properly corresponds to the ability of the network to undergo bond exchanges [49]. This value effectively represents the onset of a rearrangement that is exclusively dependent on the chemistry of the system (equivalently, independent of the applied external load).…”

Section: Vitrimersmentioning

confidence: 99%

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The Impact of Vitrimers on the Industry of the Future: Chemistry, Properties and Sustainable Forward-Looking Applications

2020

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Thermosets are known to be very reliable polymeric materials for high-performance and light-weight applications, due to their retained dimensional stability, chemical inertia and rigidity over a broad range of temperatures. However, once fully cured, they cannot be easily reshaped or reprocessed, thus leaving still unsolved the issues of recycling and the lack of technological flexibility. Vitrimers, introduced by Leibler et al. in 2011, are a valiant step in the direction of bridging the chasm between thermoplastics and thermosets. Owing to their dynamic covalent networks, they can retain mechanical stability and solvent resistance, but can also flow on demand upon heating. More generally, the family of Covalent Adaptable Networks (CANs) is gleaming with astounding potential, thanks to the huge variety of chemistries that may enable bond exchange. Arising from this signature feature, intriguing properties such as self-healing, recyclability and weldability may expand the horizons for thermosets in terms of improved life-span, sustainability and overall enhanced functionality and versatility. In this review, we present a comprehensive overview of the most promising studies featuring CANs and vitrimers specifically, with particular regard for their industrial applications. Investigations into composites and sustainable vitrimers from epoxy-based and elastomeric networks are covered in detail.

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Section: Vitrimersmentioning

confidence: 93%

Section: Vitrimersmentioning

confidence: 99%

Section: Vitrimersmentioning

confidence: 99%

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The Impact of Vitrimers on the Industry of the Future: Chemistry, Properties and Sustainable Forward-Looking Applications

2020

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Section: Figurementioning

confidence: 99%

“…Above the topology freezing transition, with its temperature denoted as T v , the exchange reactions become macroscopically relevant and the network is able to flow and to fully relax stresses. [4,5] Leibler et al coined the term vitrimer, as the related decrease in viscosity follows the Arrhenius law and is similar to strong glass-forming liquids. This pioneering work has further become the starting point for numerous studies on epoxy-based By cleavage of the o-NBE groups upon irradiation with ultraviolet (UV) light, positive tone micropatterns were conveniently inscribed by photolithography.…”

mentioning

confidence: 99%

Photopatternable and Rewritable Epoxy‐Anhydride Vitrimers

Giebler

Alabiso

Wieser

et al. 2020

Macromol. Rapid Commun.

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The present work highlights a new approach to write, erase, and rewrite micropatterns into the same region of covalent adaptable polymer networks. Thermal curing of an epoxy‐terminated o‐nitrobenzyl ester (o‐NBE) derivative with hexahydrophthalic anhydride in the presence of 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene yields a dynamic covalent network, whose solubility is locally controlled by irradiation with ultraviolet (UV) light. The photolysis of the o‐NBE chromophores enables a well‐defined cleavage of the epoxy‐anhydride network, and the formation of soluble photolysis products is confirmed by sol‐gel analysis. The photo‐induced change in solubility is exploited to inscribe micropatterns by photolithographic techniques and after development in an organic solvent positive tone structures with a feature size of 20 µm are obtained. Due to the thermo‐activated exchange reactions of the hydroxyl ester links and the related macroscopic reflow, the polymer patterns are fully erased at temperatures well above the topological freezing transition of the vitrimer network. The regenerated film has a smooth surface topology and can be reused to inscribe new micropatterns via mask lithography.

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AI‐Guided Inverse Design and Discovery of Recyclable Vitrimeric Polymers

Zheng,

Thakolkaran,

Biswal

et al. 2024

Advanced Science

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Vitrimer is a new, exciting class of sustainable polymers with healing abilities due to their dynamic covalent adaptive networks. However, a limited choice of constituent molecules restricts their property space and potential applications. To overcome this challenge, an innovative approach coupling molecular dynamics (MD) simulations and a novel graph variational autoencoder (VAE) model for inverse design of vitrimer chemistries with desired glass transition temperature (Tg) is presented. The first diverse vitrimer dataset of one million chemistries is curated and Tg for 8,424 of them is calculated by high‐throughput MD simulations calibrated by a Gaussian process model. The proposed VAE employs dual graph encoders and a latent dimension overlapping scheme which allows for individual representation of multi‐component vitrimers. High accuracy and efficiency of the framework are demonstrated by discovering novel vitrimers with desirable Tg beyond the training regime. To validate the effectiveness of the framework in experiments, vitrimer chemistries are generated with a target Tg = 323 K. By incorporating chemical intuition, a novel vitrimer with Tg of 311–317 K is synthesized, experimentally demonstrating healability and flowability. The proposed framework offers an exciting tool for polymer chemists to design and synthesize novel, sustainable polymers for various applications.

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The crucial role of external force in the estimation of the topology freezing transition temperature of vitrimers by elongational creep measurements

Cited by 49 publications

References 25 publications

The Impact of Vitrimers on the Industry of the Future: Chemistry, Properties and Sustainable Forward-Looking Applications

The Impact of Vitrimers on the Industry of the Future: Chemistry, Properties and Sustainable Forward-Looking Applications

Photopatternable and Rewritable Epoxy‐Anhydride Vitrimers

AI‐Guided Inverse Design and Discovery of Recyclable Vitrimeric Polymers

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