Healing of Polymeric Solids by Supramolecular Means

Neumann, Laura N.; Weder, Christoph; Schrettl, Stephen

doi:10.2533/chimia.2019.277

Cited by 8 publications

(7 citation statements)

References 40 publications

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“…In addition to the nature of the binding motifs and the usually telechelic polymer core employed to connect them into (macro)monomers, effects such as the aggregation, phase separation, glass formation, or crystallization of the binding motifs or the telechelic core significantly influence the properties of supramolecular polymers in the solid state, particularly by restricting the molecular mobility in the system. − The formation of lamellar morphologies has been reported for several MSPs, including materials made by assembling 2,6-bis(1′-methylbenzimidazolyl)pyridine (Mebip) end-capped telechelic penta(ethylene glycol) or poly(tetrahydrofuran) macromonomers with Zn(ClO 4 ) 2 , Mebip-terminated poly(ethylene- co -butylene) with Zn(NTf 2 ) 2 or La(NTf 2 ) 2 , and Mebip-terminated poly(tetrahydrofuran) with mixtures of Zn(ClO 4 ) 2 and Eu(ClO 4 ) 3 . In all of these materials, crystalline or glassy (solid amorphous) hard domains formed by the binding motifs act as physical cross-links at ambient temperatures, while the telechelic cores form a low-glass-transition soft phase.…”

Section: Introductionmentioning

confidence: 99%

Structure–Property Relationships of Microphase-Separated Metallosupramolecular Polymers

et al. 2020

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The structural, thermomechanical, and viscoelastic properties of metallosupramolecular polymers (MSPs) can be controlled through the choice of the multiligand monomer and the nature of the metal salt from which these materials are assembled. This versatility and the dynamic nature of certain metal–ligand (ML) complexes make MSPs very interesting for the design of stimuli-responsive materials. We here report on the investigation of the structure–property relationships of MSPs based on a macromonomer formed by terminating telechelic poly(ethylene-co-butylene) (PEB) with 2,6-bis(1′-methylbenzimidazolyl)pyridine (Mebip) ligands and transition metal or lanthanoid salts. The nature of the metal ion (Zn2+, Fe2+, Tb3+, La3+, or Gd3+), the counterion (trifluoromethanesulfonate (OTf–), perchlorate (ClO4 –), or bis(trifluoromethylsulfonyl)imide (NTf2 –)), and the number-average molecular weight (M n) of the PEB core (2100 or 3100 g mol–1) were systematically varied with the aim to provide an improved understanding of how these parameters influence the properties. In all MSPs, the polar ML complexes and the nonpolar PEB were found to microphase separate into lamellar or hexagonal morphologies with a soft PEB phase and a ML hard phase. The microstructure formation and the mechanical properties were significantly influenced by the coordination geometry of the metal–ligand complexes as well as the volume fraction of the ML phase. The nature of the metal and counterions further affected the glass or melting transitions of the hard phase. In general, lower softening temperatures were observed for the MSPs made with lanthanoid salts. Measurements of the frequency-dependent oscillatory shear moduli were used to study the relaxation processes in the different MSPs and allowed determining the activation energy of the ML complexes in lanthanoid-based MSPs.

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Section: Introductionmentioning

confidence: 99%

Structure–Property Relationships of Microphase-Separated Metallosupramolecular Polymers

et al. 2020

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“…Therefore, the factors influencing the properties of metallosupramolecular elastomers have their unique complexity. Studies on supramolecular elastomers have shown that the overall performance of the materials depends more on the kinetic properties rather than the association constants of the supramolecular interactions. − In addition, the properties of solid supramolecular elastomers are also significantly affected by microscopic structures such as network morphology, aggregation, phase separation, and crystallization. − …”

Section: Introductionmentioning

confidence: 99%

Effect of Counterions on the Physicomechanical Properties of Copper–Nitrogen-Coordinated Metallosupramolecular Elastomers

Liu

et al. 2022

ACS Appl. Mater. Interfaces

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Metallosupramolecular elastomers have attracted much attention due to their excellent mechanical properties, flexible tailoring of performance, and responsiveness to photo and thermal stimuli. The physicomechanical properties of metallosupramolecular elastomers are highly dependent on metal salts and ligand units; however, the role of counterions lacks practical exploration. To this end, we synthesized a simple acrylate copolymer model and introduced copper salts with different counterions to construct dynamic copper–nitrogen coordination cross-linked networks. This approach generated a series of elastomers with a tensile strength of over 10 MPa and a laser self-healing efficiency of over 90% within 2 min. In particular, we studied the effects of counterions on the thermodynamic, viscoelastic, mechanical, photothermal, and self-healing properties of the materials. Therefore, this work can provide instruction for the preparation and performance tailoring of metallosupramolecular elastomers.

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“…For example, directional noncovalent interactions such as hydrogen bonds, π-attractive forces, and metal-ligand interactions generally respond to external stimuli in a reversible manner. [32][33][34][35][36] When employed in polymers, the motifs can not only provide nonsacrificial pathways for the dissipation of energy in response to mechanical deformation, but also endow the host material with a plethora of other properties and functions such as healing capabilities, [33,[35][36][37] enhanced toughness, [38] and improved melt-processing characteristics. [32,39] Furthermore, noncovalent binding motifs can be designed to feature a very wide range of interaction strengths, with association constants (K a ) varying from relatively low values of ≈10 2 M −1 for, e.g., double hydrogen-bonding motifs, up to very high association constants of ≈10 14 M −1 for the interaction in complexes of tridentate ligands and metal-ions.…”

Section: Introductionmentioning

confidence: 99%

From Molecules to Polymers—Harnessing Inter‐ and Intramolecular Interactions to Create Mechanochromic Materials

Traeger

Kiebala

Weder

et al. 2020

Macromol. Rapid Commun.

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tion occurs to avoid catastrophic materials failure and to possibly redirect degradation processes into useful responses. Consequently, research efforts directed toward the investigation and development of mechanoresponsive materials has drawn ever increasing attention. [2,3,5-8] Polymers that translate mechanical stresses into a defined response are thought to be useful for many different applications, including as tamper-proof packaging materials, [9] as degradable plastics, [10,11] or for structural health monitoring. [12] One possibility to render polymers mechanoresponsive is the integration of so-called mechanophores. The latter generally feature a weak covalent bond that undergoes either homo-or heterolytic cleavage upon experiencing a force that exceeds a certain threshold. [1,5,7,13,14] These motifs are covalently incorporated into a polymer and serve as predefined weak links that preferentially break or transform in response to an applied mechanical force. [1,6,14-16] Widely investigated mechanophores include spiropyrans, 1,2-dioxetanes, and Diels-Alder adducts. [16-18] The rate constants, threshold forces, and transition state bond-lengths and energies of many mechanophores have been well-characterized via techniques such as single-molecule force spectroscopy (SMFS), [19-22] force-modified potential energy surface modeling, [23] and in situ activation using sonication. [2,22,24] The insights gained in such studies have driven advancements in the field of mechanoresponsive materials and the mechanical activation has, for example, been harnessed to promote thermodynamically unfavorable reactions, [19] affect the intra-or intermolecular transfer of protons, [20,25,26] release small molecules, [27] initiate the depolymerization of the surrounding material, [10,28] or elicit changes in the material's color or fluorescence. [16,17,29] The fact that the active bond or functional group of a mechanophore is typically cleaved irreversibly can limit its utility. Some mechanophores can be returned to their original state through an additional stimulus such as light or heat, but unless the mechanophore undergoes a nonscissile cleavage (e.g., a ring-opening reaction, such as in spiropyrans), the reversal is generally hampered by kinetic factors that leave the mechanophore in its cleaved state. [30] An irreversible response can be desirable for some

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Healing of Polymeric Solids by Supramolecular Means

Cited by 8 publications

References 40 publications

Structure–Property Relationships of Microphase-Separated Metallosupramolecular Polymers

Structure–Property Relationships of Microphase-Separated Metallosupramolecular Polymers

Effect of Counterions on the Physicomechanical Properties of Copper–Nitrogen-Coordinated Metallosupramolecular Elastomers

From Molecules to Polymers—Harnessing Inter‐ and Intramolecular Interactions to Create Mechanochromic Materials

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