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Dynamic bonds are a powerful approach to tailor the mechanical properties of elastomers and introduce shape-memory, self-healing, and recyclability. Among the library of dynamic crosslinks, electrostatic interactions among oppositely charged ions have been shown to enable tough and resilient elastomers and hydrogels. In this work, we investigate the mechanical properties of ionically crosslinked ethyl acrylate-based elastomers assembled from oppositely charged copolymers. Using both infrared and Raman spectroscopy, we confirm that ionic interactions are established among polymer chains. We find that the glass transition temperature of the complex is in between the two individual copolymers, while the complex demonstrates higher stiffness and more recovery, indicating that ionic bonds can strengthen and enhance recovery of these elastomers. We compare cycles to increasing strain levels at different strain rates, and hypothesize that at fast strain rates ionic bonds dynamically break and reform while entanglements do not have time to slip, and at slow strain rates ionic interactions are disrupted and these entanglements slip significantly. Further, we show that a higher ionic to neutral monomer ratio can increase the stiffness, but its effect on recovery is minimal. Finally, taking advantage of the versatility of acrylates, ethyl acrylate is replaced with the more hydrophilic 2-hydroxyethyl acrylate, and the latter is shown to exhibit better recovery and self-healing at a cost of stiffness and strength. The design principles uncovered for these easy-to-manufacture polyelectrolyte complex-inspired bulk materials can be broadly applied to tailor elastomer stiffness, strength, inelastic recovery, and self-healing for various applications.
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Bulk network polymers with dynamic B–O bonds: healable and reprocessable materials
The need to minimize the amount of polymeric waste entering landfills and oceans has led to several research avenues in the field of polymer science. Particularly, the development of intrinsically self-healing and reprocessable thermoset polymers containing dynamic crosslinks has garnered significant interest in the recent years. Reversible B–O bonds in certain orgonoboron compounds have shown great versatility and promise as dynamic crosslinks for the design of self-healing and reprocessable bulk polymer networks. This review provides an overview of the chemistry of organoboron species with dynamic B–O bonds amenable to the design of healable/reprocessable thermosets. Recent developments in this fairly young and interesting research topic are highlighted, along with a critical commentary on the scope and future challenges in designing robust dynamic materials with reversible B–O bonds.
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- Award ID(s):
- 1904631
- PAR ID:
- 10157074
- Date Published:
- Journal Name:
- Materials Horizons
- Volume:
- 7
- Issue:
- 3
- ISSN:
- 2051-6347
- Page Range / eLocation ID:
- 694 to 714
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c9mh01223k
