Double-Network Strategy Improves Fracture Properties of Chondroitin Sulfate Networks

Suekama, Tiffany C.; Hu, Jian; Kurokawa, Takayuki; Gong, Jian Ping; Gehrke, Stevin H.

doi:10.1021/mz3006318

Cited by 102 publications

(112 citation statements)

References 22 publications

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“…[ 25 ] Thus, the internal fracture process of the fi rst network is considered to be critical for toughness enhancement, because relatively large damage zones formed in the fi rst network allow for more accumulated damage before macroscopic crack propagation occurs throughout whole networks. [ 26,27 ] Double network (DN) hydrogels with two strong asymmetric networks being chemically linked have demonstrated their excellent mechanical properties as the toughest hydrogels, but chemically linked DN gels often exhibit negligible fatigue resistance and poor self-healing property due to the irreversible chain breaks in covalent-linked networks. Here, a new design strategy is proposed and demonstrated to improve both fatigue resistance and self-healing property of DN gels by introducing a ductile, nonsoft gel with strong hydrophobic interactions as the second network.…”

mentioning

confidence: 99%

A Novel Design Strategy for Fully Physically Linked Double Network Hydrogels with Tough, Fatigue Resistant, and Self‐Healing Properties

Chen

Zhu

Chen

et al. 2015

Adv Funct Materials

555

376

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1 wileyonlinelibrary.com recoverability and self-healing property, due to their intrinsic structural heterogeneity and/or lack of effi cient energydissipation mechanisms, [ 13 ] which greatly limit their uses for other applications requiring highly mechanical properties such as cartilage, tendon, muscle, and blood vessel.Many efforts have been made to develop tough hydrogels with new microstructures and toughening mechanisms, such as double network hydrogels, [ 14 ] nanocomposite hydrogels, [ 15 ] sliding-ring hydrogels, [ 16 ] macromolecular microsphere composite hydrogels, [ 17 ] tetrapolyethylene glycol hydrogels, [ 18 ] hydrophobically associated hydrogels, [ 19,20 ] and dipole-dipole or hydrogen bonding enhanced hydrogels. [ 21,22 ] Among them, double network (DN) hydrogels have demonstrated their excellent mechanical properties. The existing knowledge of DN gels from synthesis methods, network structures, to toughening mechanisms mainly comes from chemically cross-linked DN gels. [ 23 ] Both networks with contrasting structures in DN gels are separately crosslinked by covalent bonds, [ 24 ] and the interpenetration of two contrasting networks makes the chemically linked DN gels both tough and soft, as evidenced by stiffness (elastic modulus of 0.1-1.0 MPa), strength (failure tensile stress of 1-10 MPa, strain 1000%-2000%, failure compressive stress 20-60 MPa, strain 90%-95%), and toughness (tearing fracture energy of 10 2 -10 3 J m −2 ). [ 23 ] Chemically linked DN gels have comparable toughness to cartilage and rubber. The toughening mechanisms are largely based on "sacrifi cial bonds" that break from the fi rst network to effectively dissipate energy, protect the second network, sustain stress, and store elastic energy, thus to reinforce the gels. However, the fracture of the fi rst network also causes irreversible and permanent bond breaks, making the gels very diffi cult to be repaired and recovered from damages and fatigues. [ 25 ] Thus, the internal fracture process of the fi rst network is considered to be critical for toughness enhancement, because relatively large damage zones formed in the fi rst network allow for more accumulated damage before macroscopic crack propagation occurs throughout whole networks. [ 26,27 ] Double network (DN) hydrogels with two strong asymmetric networks being chemically linked have demonstrated their excellent mechanical properties as the toughest hydrogels, but chemically linked DN gels often exhibit negligible fatigue resistance and poor self-healing property due to the irreversible chain breaks in covalent-linked networks. Here, a new design strategy is proposed and demonstrated to improve both fatigue resistance and self-healing property of DN gels by introducing a ductile, nonsoft gel with strong hydrophobic interactions as the second network. Based on this design strategy, a new type of fully physically cross-linked Agar/hydrophobically associated polyacrylamide (HPAAm) DN gels are synthesized by a simple one-pot method. Agar/ HPAAm DN gels exhibit excellent mech...

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mentioning

confidence: 99%

A Novel Design Strategy for Fully Physically Linked Double Network Hydrogels with Tough, Fatigue Resistant, and Self‐Healing Properties

Chen

Zhu

Chen

et al. 2015

Adv Funct Materials

555

376

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“…[5][6][7][8][9] Many experimental and theoretical studies have been performed to reveal the toughening mechanism of the DN gels. [10][11][12][13] These studies have revealed that the high toughness of DN gels derives from the internal fracture of the brittle network during deformation, which is observed by yielding, necking, and irreversible softening (the Mullins effect) phenomena upon tensile deformation.…”

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confidence: 99%

Brittle–ductile transition of double network hydrogels: Mechanical balance of two networks as the key factor

Ahmed

Nakajima

Kurokawa

et al. 2014

Polymer

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133

159

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Tough double network (DN) hydrogels are a kind of interpenetrating network (IPN) gels with a contrasting structure; it consists of a rigid and brittle 1 st network with dilute, densely cross-linked short chains and a soft and ductile 2 nd network with concentrated, loosely cross-linked long chains. In this work, we focus on how the brittle gel changes into a tough one by increasing the amount of ductile component. By comparing the molecular structures of the individual first network and second network gels, we found that the true key factor that controls the brittleductile transition is the density of elastically effective polymer strands of the two networks, and . When / < 1, the second network fractures right after the fracture of the first network, and the gels are brittle. When / > 1, only the first network fractures. As a result, the brittle first network serves as sacrificial bonds, imparting toughness of DN gels. This result provides essential information to design tough materials based on the double network concept.3

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“…The multicomponent structure of this gel allowed changes in the stress response in different deformation modes, as seen in cartilage. 46 In the following subsections, we will introduce the methods that have been used to evaluate the toughness of hydrogels in general. However, in an effort to determine a reliable method for toughness measurement of hydrogels in cartilage regeneration, we will discuss only the methods that can be applied to both hydrogels and cartilage.…”

Section: Fracture Toughness Measurement Of Hydrogelsmentioning

confidence: 99%

Mechanical Testing of Hydrogels in Cartilage Tissue Engineering: Beyond the Compressive Modulus

Xiao

Friis

Gehrke

et al. 2013

Tissue Engineering Part B: Reviews

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Double-Network Strategy Improves Fracture Properties of Chondroitin Sulfate Networks

Cited by 102 publications

References 22 publications

A Novel Design Strategy for Fully Physically Linked Double Network Hydrogels with Tough, Fatigue Resistant, and Self‐Healing Properties

A Novel Design Strategy for Fully Physically Linked Double Network Hydrogels with Tough, Fatigue Resistant, and Self‐Healing Properties

Brittle–ductile transition of double network hydrogels: Mechanical balance of two networks as the key factor

Mechanical Testing of Hydrogels in Cartilage Tissue Engineering: Beyond the Compressive Modulus

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