Sacrificial Mechanical Bond is as Effective as a Sacrificial Covalent Bond in Increasing Cross-Linked Polymer Toughness.

Yokochi, Hirogi ORCID: 0009-0005-3887-762X, O'Neill, Robert T ORCID: 0000-0002-4348-7635, Abe, Takumi, Aoki, Daisuke ORCID: 0000-0002-7272-0643, Boulatov, Roman ORCID: 0000-0002-7601-4279 and Otsuka, Hideyuki ORCID: 0000-0002-1512-671X (2023) Sacrificial Mechanical Bond is as Effective as a Sacrificial Covalent Bond in Increasing Cross-Linked Polymer Toughness. Journal of the American Chemical Society, 145 (43). pp. 23794-23801.

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Official URL: http://dx.doi.org/10.1021/jacs.3c08595

Abstract

Sacrificial chemical bonds have been used effectively to increase the toughness of elastomers because such bonds dissociate at forces significantly below the fracture limit of the primary load-bearing bonds, thereby dissipating local stress. This approach owes much of its success to the ability to adjust the threshold force at which the sacrificial bonds fail at the desired rate, for example, by selecting either covalent or noncovalent sacrificial bonds. Here, we report experimental and computational evidence that a mechanical bond, responsible for the structural integrity of a rotaxane or a catenane, increases the elastomer's fracture strain, stress, and energy as much as a covalent bond of comparable mechanochemical dissociation kinetics. We synthesized and studied 6 polyacrylates cross-linked by either difluorenylsuccinonitrile (DFSN), which is an established sacrificial mechanochromic moiety; a [2]rotaxane, whose stopper allows its wheel to dethread on the same subsecond time scale as DFSN dissociates when either is under tensile force of 1.5-2 nN; a structurally homologous [2]rotaxane with a much bulkier stopper that is stable at force >5.5 nN; similarly stoppered [3]rotaxanes containing DFSN in their axles; and a control polymer with aliphatic nonsacrificial cross-links. Our data suggest that mechanochemical dethreading of a rotaxane without failure of any covalent bonds may be an important, hitherto unrecognized, contributor to the toughness of some rotaxane-cross-linked polymers and that sacrificial mechanical bonds provide a mechanism to control material fracture behavior independently of the mechanochemical response of the covalent networks, due to their distinct relationships between structure and mechanochemical reactivity.

Item Type:	Article
Uncontrolled Keywords:	Bioengineering
Divisions:	Faculty of Science and Engineering > School of Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	10 Nov 2023 15:35
Last Modified:	14 Mar 2024 20:03
DOI:	10.1021/jacs.3c08595
Open Access URL:	https://doi.org/10.1021/jacs.3c08595
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3176735