Bond strength regime dictates stress relaxation behavior

Sacligil, Ipek; Barney, Christopher W.; Crosby, Alfred J.; Tew, Gregory N.

doi:10.1039/d2sm00499b

Cited by 8 publications

(4 citation statements)

References 48 publications

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“…Examples include double networks, , host–guest interactions, , hydrogen bonding, and metal–ligand interactions, , with metal–ligand systems having the added advantage of tunability via the strength and nature of the metal–ligand bond. This feature allows network stiffness and relaxation properties to be controlled through careful selection of metal–ligand dissociation times. ,− …”

Section: Introductionmentioning

confidence: 99%

Modular Synthesis and Patterning of High-Stiffness Networks by Postpolymerization Functionalization with Iron–Catechol Complexes

et al. 2023

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Bioinspired iron–catechol cross-links have shown remarkable success in increasing the mechanical properties of polymer networks, in part due to clustering of Fe3+–catechol domains which act as secondary network reinforcing sites. We report a versatile synthetic procedure to prepare modular PEG-acrylate networks with independently tunable covalent bis(acrylate) and supramolecular Fe3+–catechol cross-linking. Initial control of network structure is achieved through radical polymerization and cross-linking, followed by postpolymerization incorporation of catechol units via quantitative active ester chemistry and subsequent complexation with iron salts. By tuning the ratio of each building block, dual cross-linked networks reinforced by clustered iron–catechol domains are prepared and exhibit a wide range of properties (Young’s moduli up to ∼245 MPa), well beyond the values achieved through purely covalent cross-linking. This stepwise approach to mixed covalent and metal–ligand cross-linked networks also permits local patterning of PEG-based films through masking techniques forming distinct hard, soft, and gradient regions.

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Section: Introductionmentioning

confidence: 99%

Modular Synthesis and Patterning of High-Stiffness Networks by Postpolymerization Functionalization with Iron–Catechol Complexes

et al. 2023

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“…They are known to affect the bandgap, leading to structural instability, an increase in defect density, reduced carrier mobility, increased ionic mobility, higher risk of cracking or mechanical failure, and lower cell efficiency. − As shown in Figure a, an applied tensile stress can cause the perovskite film to break down into a yellow PbI 2 phase and create a path for rapid ion migration, which might relieve some of the thermally induced stress. Stress relaxation is a common effect seen in different classes of materials and is ascribed to the breaking of bonds in metals or the movement of polymer chains in elastic fibers . Previous research on stress in perovskite solar cells has shown that tension leads to an increase in ion migration and accelerates breakdown of methylammonium lead iodide to lead iodide .…”

Section: Introductionmentioning

confidence: 99%

Tuning Film Stresses for Open-Air Processing of Stable Metal Halide Perovskites

Ahmad,

Cartledge,

McAndrews

et al. 2023

ACS Appl. Mater. Interfaces

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Challenges to upscaling metal halide perovskites (MHPs) include mechanical film stresses that accelerate degradation, dominate at the module scale, and can lead to delamination or fracture. In this work, we demonstrate open-air blade coating of single-step coated perovskite as a scalable method to control residual film stress after processing and introduce beneficial compression in the thin film with the use of polymer additives such as gellan gum and corn starch. The optoelectronic properties of MHP films with compression are improved with higher photoluminescence yields. MHP film stability is significantly improved under compression, under humidity, heat, and thermal cycling. By measuring the evolution of film stresses, we demonstrate for the first time that stress relaxation occurs in MHP films with tensile stress that correlates with film degradation. This discovery of a new mechanism underpinning MHP degradation shows that film stress can be used as a parameter to screen MHP devices and modules for quality control before deployment as a design for reliability criterion.

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“…[1][2][3][4] Herein, the chemical bonds holding the network together are no longer static and permanent, but dynamic, where they break and reform at appropriate processing conditions. The use of non-covalent bonds, 5,6 dynamic covalent bonds, [7][8][9] and combinations thereof 10,11 has been explored in detail to achieve such dynamic properties. These investigations not only elucidated the different mechanisms by which bond exchange reactions can occur, 12 either associative or dissociative, but also highlighted the importance of the nature of the chemical bond, 5,13 the network topology, 14,15 and the time scales at which relaxation processes occur.…”

Section: Introductionmentioning

confidence: 99%

“…The use of non-covalent bonds, 5,6 dynamic covalent bonds, [7][8][9] and combinations thereof 10,11 has been explored in detail to achieve such dynamic properties. These investigations not only elucidated the different mechanisms by which bond exchange reactions can occur, 12 either associative or dissociative, but also highlighted the importance of the nature of the chemical bond, 5,13 the network topology, 14,15 and the time scales at which relaxation processes occur. 1,3,16,17 Non-covalent bonds such as hydrogen bonds, for example, show fast relaxation processes at higher temperatures, whereas those of their dynamic covalent counterparts are much slower.…”

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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Bond strength regime dictates stress relaxation behavior

Abstract: This work utilizes in situ crosslinked dynamic networks to show differences in stress-relaxation behavior depending on the bond strength of the metal–ligand crosslinker used.

Cited by 8 publications

References 48 publications

Modular Synthesis and Patterning of High-Stiffness Networks by Postpolymerization Functionalization with Iron–Catechol Complexes

Modular Synthesis and Patterning of High-Stiffness Networks by Postpolymerization Functionalization with Iron–Catechol Complexes

Tuning Film Stresses for Open-Air Processing of Stable Metal Halide Perovskites

Dynamic covalent networks with tunable dynamicity by mixing acylsemicarbazides and thioacylsemicarbazides

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