Multiscale Energy Dissipation Mechanism in Tough and Self-Healing Hydrogels

Cui, Kunpeng; Sun, Tao Lin; Liang, Xiaobin; Nakajima, Ken; Ye, Yanan; Liang, Chengyao; Kurokawa, Takayuki; Gong, Jian Ping

doi:10.1103/physrevlett.121.185501

Cited by 121 publications

(162 citation statements)

References 30 publications

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“…As shown in Fig. 2A, SAXS images of the samples show an isotropic ring and a peak in one-dimensional (1D) scattering profiles, attributed to the bicontinuous phase networks consisting of a soft network (with a low modulus) and a hard network (with a high modulus) (28,29). The intensity of the peak I m significantly increases with the increase of T dial .…”

Section: Resultsmentioning

confidence: 85%

“…The opposite charges on the polymer chains form ionic bonds when the small counter ions (Na + and Cl − ) are removed from the PA gels by dialysis of the samples in pure water. The formation of these ionic bonds induces local aggregation of the polymers, and as a result the gels form a dense hard phase and sparse soft phase interconnected at ∼100-nm scale (28). Such a structure acts as bicontinuous hard/soft phase networks.…”

Section: Resultsmentioning

confidence: 99%

“…In regime II, d ⊥ /d 0 decreases slowly and deviates from affine deformation. In this regime, the first loading sample softens but fully shrinks back to its original size after a sufficiently long waiting time, which indicates that the hard phase network ruptures, while the soft phase network stays intact, providing the entropic restoring force (28). In regime III, d ⊥ /d 0 increases slightly with λ, and the failure of the whole sample occurs soon thereafter, by rupture of the soft phase network.…”

Section: Respectively With the Global Elongation Ratio λmentioning

confidence: 97%

“…These PA gels, containing ionic bonds at the 1-nm scale, a cross-linked polymer network at the 10-nm scale, and isotropic bicontinuous hard/soft phase networks at the 100-nm scale ( Fig. 1), exhibit a multiscale response to loads and dissipate large amounts of energy to show a very high toughness (28). Such hierarchical structures make the PA gels good candidates as a simple model system to study the effect of hierarchical structures on the fatigue behavior of self-healing materials containing abundant noncovalent bonds.…”

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confidence: 99%

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Mesoscale bicontinuous networks in self-healing hydrogels delay fatigue fracture

Cui

Sun

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Load-bearing biological tissues, such as muscles, are highly fatigue-resistant, but how the exquisite hierarchical structures of biological tissues contribute to their excellent fatigue resistance is not well understood. In this work, we study antifatigue properties of soft materials with hierarchical structures using polyampholyte hydrogels (PA gels) as a simple model system. PA gels are tough and self-healing, consisting of reversible ionic bonds at the 1-nm scale, a cross-linked polymer network at the 10-nm scale, and bicontinuous hard/soft phase networks at the 100-nm scale. We find that the polymer network at the 10-nm scale determines the threshold of energy release rateG0above which the crack grows, while the bicontinuous phase networks at the 100-nm scale significantly decelerate the crack advance until a transitionGtranfar aboveG0. In situ small-angle X-ray scattering analysis reveals that the hard phase network suppresses the crack advance to show decelerated fatigue fracture, andGtrancorresponds to the rupture of the hard phase network.

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Section: Resultsmentioning

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Section: Respectively With the Global Elongation Ratio λmentioning

confidence: 97%

mentioning

confidence: 99%

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Mesoscale bicontinuous networks in self-healing hydrogels delay fatigue fracture

Cui

Sun

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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107

101

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“…By dialysis of small counterions in pure water, ionic associations between opposite charges on the polymer chains, both intrachain and interchain, are switched on, forming a bicontinuous network structure, consisting a soft network (with low modulus) and a hard network (with high modulus), of ~100 nm in scale. 30 Figure 1a presents the pictures of PA hydrogels after re-equilibration in PEG solutions with different PEG concentrations. The initial sizes of the gels are the same with a 10 mm diameter and a 1.9 mm thickness.…”

Section: Resultsmentioning

confidence: 99%

Effect of Structure Heterogeneity on Mechanical Performance of Physical Polyampholytes Hydrogels

Cui

Sun

et al. 2019

Macromolecules

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Recent studies reported multiscale structure in tough and self-healing hydrogels containing physical associations. For example, a type of tough and self-healing hydrogels from charged balanced polyampholytes (PA) have a meso-scale bicontinuous double network structure with structural length around 400 nm. This meso-scale network structure plays an essential role in the multistep rupture process, which leads to the high toughness of PA hydrogels. In this work, by using an osmotic stress method, we symmetrically studied how the relative strength of soft and hard networks and the strength of ionic bonds influence the property of PA gels. We found that, increasing osmotic stress of the bath solution triggers the structure transition from bicontinuous double network structure to a homogeneous structure, which drives the concurrently opaque-transparent transition in optical property, and viscoelastic-glassy transition in mechanical behavior. The gels around the structural transition point were found to possess both high toughness (fracture energy of 7200 J m-2) and high stiffness (Young's modulus of 12.9 MPa), which is a synergy of soft network and hard network of the bicontinuous structure. Our work not only provides an approach to tune the structure and property of physical hydrogels through tuning physical association, but also gives a demo to investigate their relationships, yet another step forward, gives inspiration to design new type of tough and self-healing materials around the structural transition point.

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Tough Hydrogels Based on Sacrificial Bond Principle

Cui¹,

Gong²

2022

Macromolecular Engineering

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Hydrogels are swollen polymer networks in water and are usually considered as a type of mechanically weak materials. In recent years, by using sacrificial bond principle, many strong and tough hydrogels were developed, widely extending their application to various fields. The sacrificial bonds break preferentially during deformation, dissipating a significant amount of energy and giving a high toughness of the hydrogels. Diverse sacrificial structures have been used to toughen hydrogels, with structure length ranging from nanometer scale to millimeter scale. Different sacrificial structures cause very different specific molecular mechanisms and properties of hydrogels. In this article, the molecular mechanisms of various tough hydrogels are summarized, and the synergistic effect by combining multiple energy dissipation mechanisms to achieve super‐tough hydrogels is highlighted.

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Multiscale Energy Dissipation Mechanism in Tough and Self-Healing Hydrogels

Cited by 121 publications

References 30 publications

Mesoscale bicontinuous networks in self-healing hydrogels delay fatigue fracture

Mesoscale bicontinuous networks in self-healing hydrogels delay fatigue fracture

Effect of Structure Heterogeneity on Mechanical Performance of Physical Polyampholytes Hydrogels

Tough Hydrogels Based on Sacrificial Bond Principle

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