The double-network (DN) structure is a state-of-the-art strategy used for toughening soft materials. The challenge for widespread applications, however, is the difficulty in synthesizing the two interpenetrating networks with contrasting architecture, i.e., one network is brittle and sparse and the other is stretchable and dense. Such structures are formed to toughen hydrogels via two-step sequential synthesis of a highly swellable polyelectrolyte network and a subsequent stretchable network in aqueous media; however, this approach is not directly applicable for fabricating tough DN elastomers from low-polar polymers. Herein, we propose a polyelectrolyte approach to fabricate tough solvent-free DN elastomers comprising a hybridized brittle polyelectrolyte network and a stretchable low-polar polyacrylic network. Because polyelectrolyte networks swell significantly in high-dielectric media, the contrasting DN structure can be fabricated using an organic cosolvent with an extremely high dielectric constant. ...
Living tissues, such as muscle, autonomously grow and remodel themselves to adapt to their surrounding mechanical environment through metabolic processes. By contrast, typical synthetic materials cannot grow and reconstruct their structures once formed. We propose a strategy for developing “self-growing” polymeric materials that respond to repetitive mechanical stress through an effective mechanochemical transduction. Robust double-network hydrogels provided with a sustained monomer supply under...
In this work, we intended to investigate the relationship between the swelling ratio Q and Young's modulus E of hydrogels from their contracted state to extreme swelling state and elucidate the underlining molecular mechanism. For this purpose, we used tetra-poly(ethylene glycol) (tetra-PEG) gel, whose network parameters are well known, as the polymer backbone, and we succeeded in tuning the swelling of the gel by a factor of 1500 times while maintaining the topological structure of the network ...
A classic paradigm of soft and extensible polymer materials is the difficulty of combining reversible elasticity with high fracture toughness, in particular for moduli above 1 MPa. Our recent discovery of multiple network acrylic elastomers opened a pathway to obtain precisely such a combination. We show here that they can be seen as true molecular composites with a well–cross-linked network acting as a percolating filler embedded in an extensible matrix, so that the stress–strain curves of a fa...
Soft polymer networks have seen an explosion of recent developments motivated by new high tech applications in the biomedical field or in engineering. We present a candid and critical overview of the current understanding of the relation between the structure and molecular architecture of polymer networks and their mechanical properties, restricting ourselves to soft networks made of flexible polymers and displaying entropic elasticity. We specifically review and compare recent approaches to syn...
Plastic bioelectronics is a research field that takes advantage of the inherent properties of polymers and soft organic electronics for applications at the interface of biology and electronics. The resulting electronic materials and devices are soft, stretchable and mechanically conformable, which are important qualities for interacting with biological systems in both wearable and implantable devices. Work is currently aimed at improving these devices with a view to making the electronic-biologi...
A simple method was developed to fabricate tough hydrogels from a chemically cross-linked neutral hydrogel. Loosely cross-linked pseudo- and true-interpenetrating polymer network (IPN) hydrogels with double-, triple-, and quadruple-network structures were synthesized from acrylamide (AAm), and their mechanical properties were studied. Increasing the number of polymeric networks significantly changed the mechanical properties of pseudo-IPN hydrogels even though the chemical composition and polyme...
We have carried out systematic fracture experiments in a single edge notch geometry over a range of stretch rates on dual crosslink hydrogels made from polyvinyl alcohol chains chemically crosslinked with glutaraldehyde and physically crosslinked with borate ions. If the energy release rate necessary for crack propagation was calculated conventionally, by using the work done to deform the sample to the critical value of stretch \lambda_cwhere the crack propagates, we found that the fracture e...
Last. Kenji Urayama(Kyoto Institute of Technology)H-Index: 36
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The crack growth dynamics of the carbon-black (CB) filled elastomers is studied experimentally and analyzed while focusing on both kinetics and crack tip profiles. The CB amounts are varied to change the mechanical properties of the elastomers. Static crack growth measurements simultaneously reveal the discontinuous-like transition of the crack growth rate v between the "slow mode" (v≈10^{-5}-10^{-3} m/s) and "fast mode" (v≈10^{-1}-10^{2} m/s) in a narrow range of the input tearing energy Γ and ...
Here, the general design and properties of new multiple network elastomers with an exceptional combination of stiffness, toughness, and elasticity are reported. In this paper, it is reported in more detail how the increase in strain at break resulting from the toughening can be used to provide great insight in the large strain properties of otherwise brittle acrylic well crosslinked networks. The networks have been prepared by sequences of polymerization and swelling with monomers. The parameter...
Soft materials are materials with a low shear modulus relative to their bulk modulus and where elastic restoring forces are mainly of entropic origin. A sparse population of strong bonds connects molecules together and prevents macroscopic flow. In this review we discuss the current state of the art on how these soft materials break and detach from solid surfaces. We focus on how stresses and strains are localized near the fracture plane and how elastic energy can flow from the bulk of the mater...
Last. Chunyang Miao(Center for Advanced Materials)H-Index: 8
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Abstract null null Flexible supercapacitors are of tremendous interest to power future wearable electronics. The performance of a flexible supercapacitor strongly depends on the properties of electrode materials. In addition to the electrochemical performance, flexible electrodes must be mechanically robust or even stretchable during operation. Electrically conductive hydrogels (ECHs) are an ideal framework for flexible electrode design and construction, owing to their three-dimensional conducti...
Abstract null null Recently, research on double-network (DN) hydrogels with good biocompatibility and mechanical properties has been flourishing. The main research directions have aimed to enhance the poor mechanical properties of conventional hydrogels and to broaden their potential applications in various fields. This paper reviews the recent research progress in the preparation of DN hydrogels, including fully chemically cross-linked DN hydrogels, hybrid physically/chemically cross-linked DN ...
Abstract null null Stimuli-responsive hydrogels that can change their properties as a result of external stimuli have shown great promise in various applications, but it is still a great challenge to simultaneously provide hydrogels with excellent mechanical properties and significant response. Herein, we propose a facile synthesis of smart PAAm based hydrogels with highly elastic and swellable by introducing the activated nanoparticles into the hydrogel networks. Due to the heterogeneous microp...
Last. Xinya Zhang(SCUT: South China University of Technology)H-Index: 19
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To overcome the wearable sensor's defects and achieve the goal of robust mechanical properties, long-term adhesion, sensitive electrical conductivity, the multifunctional hydrogels were inspired by various mussels on the base of catechol and its analogues. In this review, we review the strategies for improving the mechanical strength, adhesion, conductivity and antibacterial properties of mussel-inspired hydrogels as bioelectronics. Double network structures, nanocomposites, supramolecular block...
Flexible conducting films in the forms of bendability or stretchability are developed as a key component to enable soft electronics. With the requirements of miniaturization and portability of modern electronics, conducting film that can endure in-plane shrinkage is urgently needed but still remains challenging. Here, a new type of conducting film achieving reversible in-plane folding-unfolding function with large deformation by infusing conductive liquids into hierarchically structured polymer ...
Last. Wenguang Liu(TJU: Tianjin University)H-Index: 65
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Abstract Pressure-sensitive and adhesive tapes have been widely used for many purposes. However, their intrinsically strong sticky nature and weak strength severely limits their applications to vulnerable surfaces and harsh conditions. Herein, a multifunctional tough and self-fusing elastomer tape is fabricated for the first time by simple copolymerization of a model hydrophobic monomer 2-methoxyethyl acrylate (MEA) and a model weak acid-containing monomer acrylic acid (AAc). The PMEA-PAAc copol...
We propose a new concept that utilizes the difference in Poisson's ratio between component materials as a strengthening mechanism that increases the effectiveness of the sacrificial bond toughening mechanism in macroscale double-network (Macro-DN) materials. These Macro-DN composites consist of a macroscopic skeleton imbedded within a soft elastic matrix. We varied the Poisson's ratio of the reinforcing skeleton by introducing auxetic or honeycomb functional structures that results in Poisson's ...
#1Ziyu Xing(HIT: Harbin Institute of Technology)H-Index: 3
#2Haibao Lu(HIT: Harbin Institute of Technology)H-Index: 36
Last. Yong Qing Fu(Northumbria University)H-Index: 65
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Soft elastomers with their ability to integrate strain-adaptive stiffening and coloration have recently received significant research attention for application in artificial muscle and active camouflage. However, there is a lack of theoretical understanding of their complex molecular dynamics and mechanochromic coupling/decoupling. In this study, a topological dynamics model is proposed to understand the anchoring-mediated topology signature of self-assembled elastomers. Based on the constrained...
Current synthetic elastomers suffer from the well-known trade-off between toughness and stiffness. By a combination of multiscale experiments and atomistic simulations, a transparent unfilled elastomer with simultaneously enhanced toughness and stiffness is demonstrated. The designed elastomer comprises homogeneous networks with ultrastrong, reversible, and sacrificial octuple hydrogen bonding (HB), which evenly distribute the stress to each polymer chain during loading, thus enhancing stretchab...
