Poly-1-acylsemicarbazides

Штильман, М.И.; Fedotova, O.Ya.; Kolesnikov, H.S.

doi:10.1016/0032-3950(68)90044-0

Cited by 5 publications

(3 citation statements)

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“…Acylsemicarbazide (ASC) (Figure A), regarded as a combination of urea and amide linked by a N–N bond, can be easily formed by the addition reaction between isocyanate and hydrazide . Although polyacylsemicarbazide (PASC) materials have been reported sporadically for a long time, its significant potential in polymer science has rarely been explored . Herein, we hypothesized that ASC is a dynamic moiety, which is the first stride in this study, as ASC can form an activated n-centered transition state to facilitate the transfer of protons, thereby reducing the decomposition activation energy of dynamic urea bonds .…”

Section: Introductionmentioning

confidence: 99%

“…20 Although polyacylsemicarbazide (PASC) materials have been reported sporadically for a long time, its significant potential in polymer science has rarely been explored. 21 Herein, we hypothesized that ASC is a dynamic moiety, which is the first stride in this study, as ASC can form an activated n-centered transition state to facilitate the transfer of protons, thereby reducing the decomposition activation energy of dynamic urea bonds. 22 On the other hand, ASC moieties contain several H-bond donors and acceptors and can form strong multiple H-bonds 23 such as the well-known 2-ureido-4[1H]-pyrimidinone (UPy) molecule.…”

Section: ■ Introductionmentioning

confidence: 99%

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Acylsemicarbazide Moieties with Dynamic Reversibility and Multiple Hydrogen Bonding for Transparent, High Modulus, and Malleable Polymers

Escorihuela

et al. 2020

Macromolecules

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The realization of covalent adaptable networks with excellent mechanical and dynamic properties remains a major challenge. Herein, the acylsemicarbazide (ASC) moieties with dynamic reversibility and multiple hydrogen bonding were disclosed and used to prepare transparent, high modulus, and malleable polymer networks. It was found that the ASC moiety can reversibly generate isocyanate and hydrazide at elevated temperatures, that is, exhibiting dynamic reversibility. ASC can also produce the disordered multiple hydrogen bonds that contribute to superior mechanical strength for dynamic polymers. The hydrogen bonding in ASC moieties can diminish the energy barrier for the cleavage of dynamic covalent bonds, and the dissociation of ASC moieties further promotes the disruption of hydrogen bonds, showing the synergistic dynamic effects. ASC moieties provide a valuable molecular engineering opportunity toward high-performance dynamic polymer materials. The polymer containing ASC moieties possesses excellent optical transparency, superb mechanical performance (Young's modulus up to 1.7 GPa), together with malleable and healing properties.

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Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Acylsemicarbazide Moieties with Dynamic Reversibility and Multiple Hydrogen Bonding for Transparent, High Modulus, and Malleable Polymers

Escorihuela

et al. 2020

Macromolecules

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“…ASCs are capable of multiple hydrogen bonding and, at the same time, show a tunable dynamic covalent bond character. 21 Formed by the reaction of an isocyanate and a hydrazide, the ASC motif has slowly penetrated the world of polymeric materials over the last decade, [21][22][23][24][25] with the first preparation of ASC-based polymers dating back to 1958. 26 Lehn and coworkers replaced traditionally used urethanes in linear polymer chains with ASCs and showed that the polymers formed films with elastic and self-healing properties.…”

Section: Introductionmentioning

confidence: 99%

Dynamic covalent networks with tunable dynamicity by mixing acylsemicarbazides and thioacylsemicarbazides

Sarkar

Majumdar

Kuil

et al. 2023

Journal of Polymer Science

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Dynamic covalent networks (DCNs) use chemical bonds that break and reform at appropriate processing conditions to allow reconfiguration of the networks. Recently, the acylsemicarbazide (ASC) motif has been added to the repertoire of such dynamic covalent bonds, which is capable of hydrogen bonding as well as dynamic bond exchange. In this study, we show that its sulfur congener, thioacylsemicarbazide (TASC), also acts as a dynamic covalent bond, but exchanges at a slower rate than the ASC moiety. In addition, siloxane‐based DCNs comprising either ASC or TASC motifs or a varying composition of both show tunable relaxation dynamics, which slow down with an increasing amount of TASC motifs. The reduction in stress relaxation goes hand in hand with a reduction of creep in the network and can be tuned by the ASC/TASC ratio. All networks are readily processed using compression molding and dissolve when treated with excess hydrazide in solution. The ability to control network properties and creep in dynamic covalent polymeric networks by small changes in the molecular structure of the dynamic bond allows a generalized synthetic approach while accommodating a wide temperature window for application.

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