Deformation and Fracture Behavior of Strong and Tough Hydrogels
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摘要: 水凝胶是一种在水中溶胀的聚合物网络，与生物组织具有结构上的相似性。传统水凝胶中聚合物网络的不均匀性和高含水量使得水凝胶的力学性能较弱，远远低于高强韧的生物组织，限制了其作为结构材料在生物工程等领域的应用。近年来，科研人员在提高水凝胶力学性能方面取得了很大进展，开发了很多高强韧水凝胶，如双网络（DN）水凝胶、动态键水凝胶、缠结远超交联的水凝胶和纤维复合凝胶材料等。本文首先简述了为增强水凝胶力学性能而不断进行的努力，随后介绍了水凝胶强度和韧性的关系，最后根据不同种类高强韧水凝胶的形变和破坏行为，分析其聚合物网络结构中的能量耗散机制，从而解释这些水凝胶高强韧的结构起源。Abstract: Hydrogel is a kind of polymer network swelling in water, which has structural similarity with biotissues. Traditional hydrogels are mechanically weak and brittle, due to their inherent heterogeneous microstructures and high water contents, which severely limit their applications. In recent years, researchers have been committed to improving the mechanical properties of hydrogels and have developed many strong and tough hydrogels, such as double-network (DN) hydrogels, dynamic bond hydrogels, hydrogels with rich entanglements, and fiber reinforced soft composites. In this review, we first summarize the development of hydrogels for enhancing mechanical properties and then introduce the relationship between stiffness and toughness of hydrogels. After that, several typical tough and strong hydrogels are selected to introduce their deformation and fracture behaviors, which give a preliminary understanding of the energy dissipation mechanisms of different hydrogels. The mechanisms mentioned in this paper include the breakage and reformation of physical bonds, the enhanced crack resistance due to phase-separated structure, the bulk viscoelastic energy dissipation, the near-crack dissipation and the fiber pullout and rupture. Then, the characteristics of these strong and tough hydrogels are summarized as follows: DN hydrogels dissipate energy through chain scission but soften after large deformation; dynamic bond hydrogels show self-healing behavior and large bulk hysteresis; hydrogels with rich entanglements have dense entanglements but sparse cross-links and low hysteresis; fiber reinforced soft composites have multi-scale energy dissipation and very large process zones.
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图 2 （a）凝胶形变示意图。（b）测量断裂能的纯剪切试验：（I）当初始高度为H的缺口试样拉伸到临界拉伸比λc时，裂纹开始扩展；（II）同样模式下，测量无缺口试样（除无缺口外，其他参数与缺口试样相同）的名义应力S和拉伸比λ的关系。（c）断裂一层聚合物链的本征断裂能Γ0。（d）裂纹尖端周围非弹性变形区的机械耗散对总断裂能的贡献为ΓD（机械耗散表现为应力-应变曲线上的机械回滞曲线）[20]
Figure 2. (a) Schematics of a gel during deformation. (b) The pure-shear test to measure the fracture toughness: (I) When a notched sample with initial height H is stretched by a critical ratio of λc under the pure-shear deformation, the crack begins to propagate; (II) The relationship between the nominal stress S and the stretch ratio λ is measured for an un-notched sample under the pure-shear deformation. (c) The intrinsic fracture energy Γ0 from fracturing a layer of polymer chains. (d) The mechanical dissipation in the process zone around the crack tip contributes to the total fracture energy by ΓD (The mechanical dissipation manifests as a hysteresis loop on the stress-stretch curve)[20]
图 3 （aI）DN水凝胶结构示意图；（aII）含水量（质量分数）90%的坚韧DN水凝胶图像[43]；（b）DN水凝胶的单轴拉伸应力-应变曲线以及显示颈缩过程的图片（插入字母表示应力-应变曲线及与之相对应的图片）[24]
Figure 3. (aI) Schematics of the structure of DN gels; (aII) Image to show the high toughness of a DN gel containing 90% (mass fraction) of water[43]; (b) Uniaxial tension stress-strain curves of a DN gel, and pictures to show the necking process (The insert alphabets indicate the correspondence between the stress-strain curves and the pictures)[24]
图 4 （a）DN水凝胶裂纹尖端局部损伤区的示意图[24]；（b）断链产生的自由基引发NIPAAm聚合形成PNIPAAm；（c）使用LSCM在42 ℃下观察DN水凝胶裂纹尖端获得的图像[51]
Figure 4. (a) Schematics of local damage zone at the crack front of DN gels[24]; (b) Mechanoradicals generated by chain scission initiate the polymerization of NIPAAm to form PNIPAAm; (c) Images obtained using a LSCM around the crack tip of a DN gel at 42 ℃[51]
图 5 （a）裂纹扩展试验测得的G和v的对数坐标图（箭头表示未检测到裂纹扩展的G，灰色阴影区域表示在实验分辨率（10−6 m/s）内未观察到裂纹扩展）；（b）在快速模式下，颈缩DN水凝胶和非颈缩DN-2.0-0.1水凝胶对应于图5（a）中的放大图像；（c）用剪切波速（cs）归一化的G和v的对数坐标图；（d）DN-0.8、（e）DN-2.0和（f）DN-2.0-0.1水凝胶的实时双折射观测图像（图5（d）中的白色虚线描绘了DN-0.8水凝胶的裂纹形状）；（g）颈缩DN-2.0水凝胶的裂纹尖端处对应的高延迟面积（S）和最大延迟（Rmax）对于G的曲线[52]
Figure 5. (a) Logarithmic plots of G and v measured by post-notch crack growth tests (The arrows depict the G at which crack propagation was not detected. The gray hatched regime indicates the crack propagation was not observed within experimental resolution (10−6 m/s)); (b) Magnified images of the plots shown in Fig.5(a) for the necking DN gels and unnecking DN-2.0-0.1 in the fast mode; (c) Logarithmic plots of G and v normalized by the shear wave speed cs; Real-time birefringence images of (d) DN-0.8, (e) DN-2.0 and (f) DN-2.0-0.1 (The white dashed curve in Fig.5(d) depicts the crack shape of DN-0.8); (g) Corresponding high retardation areas, S, and maximum retardations, Rmax, at the crack tips of necking DN-2.0 as a function of G[52]
图 6 （a）PA水凝胶的结构示意图[56]；（b）松弛模量G（t）随时间的变化；（c）PA水凝胶裂纹尖端的能量耗散示意图；（d）经历不同裂纹增长速率的PA水凝胶的圆偏振光双折射图像（图像拍摄于1.5的拉伸应变下）[57]
Figure 6. (a) Schematics of the structure of PA gels[56]; (b) Change of relaxation modulus G(t) with time; (c) Schematics of energy dissipation in the crack tip of PA gels; (d) Circular birefringence images of PA gels undergoing different crack growth speeds (The images were taken at a strain of 1.5)[57]
图 7 （a）名义应力（
$\sigma $ ）与拉伸比（λ）的曲线，以及几个代表性时间分辨二维SAXS图像；（b）平行于拉伸方向(∥) 和垂直于拉伸方向(⊥) 的微观变形比（d/d0）与λ的曲线；（c）形变过程中PA水凝胶的结构变化（相分离结构由硬相（绿色）和软相（红色）组成）[58]Figure 7. (a) Nominal stress (σ) versus stretch ratio (λ) and the corresponding time-resolved 2D SAXS patterns at several representative λ; (b) Microscopic deformation ratio (d/d0) in the parallel (∥) and perpendicular (⊥) directions of stretching versus λ; (c) Structure change of PA gels during deformation (The phase-separated structure composed of a stiff phase (green) and a soft phase (red))[58]
图 8 海藻酸盐-PAAm水凝胶示意图：（a）PAAm（灰线）通过N，N′-亚甲基双丙烯酰胺（MBAA，蓝色方块）共价交联形成化学交联网络；（b）海藻酸盐网络的G嵌段与Ca2+相互作用形成离子交联网络；（c）裂纹尖端区域化学交联网络的桥接作用和物理交联网络离子键的断裂重组，使得该水凝胶耗散大量能量而具有高韧性[67]
Figure 8. Schematics of alginate-PAAm gels: (a) PAAm (gray lines) forms chemically crosslinked network through N, N′-methylenebis(acrylamide) (MBAA, blue squares); (b) G blocks of the alginate network interact with Ca2+ to form an ionic crosslinked network; (c) Alginate-PAAm gels have high toughness due to a large amount of energy dissipation by the crack bridging of chemical crosslinked network and the breakage and reformation of ionic bonds of physical crosslinked network in the crack-tip region[67]
图 9 （a～c）3种断裂模型的分子机制示意图；（d）本征断裂能Γ0的链层断裂示意图，本体耗散
$\varGamma_{{\rm{D}}}^{\text{bulk}}$ 的大应力-应变滞后环，以及$\varGamma_{{\rm{D}}}^{\text{tip}}$ 的链拉出及链的离域损伤；（e）测量Γ0，Γ0+$\varGamma_{{\rm{D}}}^{\text{tip}}$ 和Γ0+$\varGamma_{{\rm{D}}}^{\text{bulk}}$ +$\varGamma_{{\rm{D}}}^{\text{tip}}$ 示意图；（f）海藻酸盐- PAAm水凝胶的3个断裂能水平[69]Figure 9. (a—c) Schematics of molecular mechanisms of three fracture models; (d) Schematic illustration of scission of a layer of chains for the intrinsic fracture energy Γ0, large stress-stretch hysteresis loop for bulk hysteretic dissipation
$\varGamma_{{\rm{D}}}^{\text{bulk}}$ , and pull-out of chains and/or delocalized damage of chains for$\varGamma_{{\rm{D}}}^{\text{tip}}$ ; (e) Schematic illustration of measuring Γ0, Γ0+$\varGamma_{{\rm{D}}}^{\text{tip}}$ and Γ0+$\varGamma_{{\rm{D}}}^{\text{bulk}}$ +$\varGamma_{{\rm{D}}}^{\text{tip}}$ ; (f) Three levels of fracture energies of the two series of alginate-PAAm hydrogels[69]
图 10 缠结远超交联的水凝胶的结构示意图：（a）凝胶中每条聚合物链都很长，且含有大量缠结点，红点表示交联点；（b）凝胶在外力下拉伸时，网链表现出张力向其他链的传递；（c）凝胶在拉伸过程中，断裂的键发生松弛，并使缠结和交联的链部分松弛（箭头表示施加的载荷）[72]
Figure 10. Schematics of the structure of hydrogels with rich entanglements; (a) Each polymer chain in the gel is very long, and has a large number of entanglements and a cross-link (red dot) at each end; (b) A stretched gel showing transmission of the tension to other chains; (c) A broken bond relaxes one chain and partly relaxes the entangled and cross-linked chains (Arrows indicate applied load)[72]
图 12 （a）左图是复合凝胶材料撕裂破坏机理示意图。撕裂区给出了3根纤维，其中纤维①支撑最大张力，纤维②在三角区的中心，纤维③刚刚进入三角区。由于拉伸强度大于摩擦力，导致纤维①和②被拉出。右图是凝胶体积收缩和溶胀对玻璃纤维影响的示意图[80]。（b）软基体-GF复合材料的撕裂能Γc对于软基体的撕裂能Γm的函数。在该图中，用作复合材料的软基体的种类包括在不同条件下的2个系列的PA坚韧水凝胶、在不同条件下的PAAm弱水凝胶和市售的聚二甲基硅氧烷（PDMS）弹性体[81]。（c）样品尺寸对PA-GF凝胶撕裂行为的影响。该图显示具有不同样品宽度的PA-GF凝胶的断裂图像，其中绿色虚线表示断裂路径，红色箭头表示纤维断裂。（d）峰值撕裂力FP和撕裂能
$\varGamma $ 随样品宽度的变化（插图编号表示撕裂图像和力学曲线之间的对应关系）[82]Figure 12. (a) Left image is a schematic of the failure mechanism of a fabric undergoing tear. Three fibers are shown, with fiber ① supporting maximum tension, fiber ② at the center of the del zone and fiber ③ just entering the del zone. The tensile strength is greater than the frictional force, resulting in fiber pullout of fibers ① and ②. Right figure is a schematic illustration of the impact of gel de-swelling and swelling on the fabric[80]. (b) Tearing energy of the soft matrix-GF composite materials, Γc, as a function of the tearing energy of the soft matrices, Γm. In this scaling plot, two series of PA tough hydrogels at different conditions, PAAm weak hydrogels at different conditions, and a commercially available polydimethylsiloxane (PDMS) elastomer are utilized as soft matrices in the composites[81]. (c) Effect of sample size on the tearing behavior of the PA-GF gels. Fracture images of the PA-GF gels with different sample width. Green dashed lines indicate the fracture path, and red arrows show the fiber fracture. (d) Changes of peak tearing force and tearing energy with sample width (The inset numbers indicate the correspondence between the fracture images and the plots)[82]
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[1] PEPPAS N A, BURES P, LEOBANDUNG W, ICHIKAWA H. Hydrogels in pharmaceutical formulations [J]. European Journal of Pharmaceutics and Biopharmaceutics,2000,50(1):27-46. doi: 10.1016/S0939-6411(00)00090-4 [2] QIU Y, PARK K. Environment-sensitive hydrogels for drug delivery [J]. Advanced Drug Delivery Reviews,2001,53(3):321-339. doi: 10.1016/S0169-409X(01)00203-4 [3] LI J Y, MOONEY D J. Designing hydrogels for controlled drug delivery [J]. Nature Reviews Materials,2016,1(12):16071. doi: 10.1038/natrevmats.2016.71 [4] LEE K Y, MOONEY D J. Hydrogels for tissue engineering [J]. Chemical Reviews,2001,101(7):1869-1879. doi: 10.1021/cr000108x [5] NGUYEN K T, WEST J L. Photopolymerizable hydrogels for tissue engineering applications [J]. Biomaterials,2002,23(22):4307-4314. doi: 10.1016/S0142-9612(02)00175-8 [6] DRURY J L, MOONEY D J. Hydrogels for tissue engineering: Scaffold design variables and applications [J]. Biomaterials,2003,24(24):4337-4351. doi: 10.1016/S0142-9612(03)00340-5 [7] DISCHER D E, JANMEY P, WANG Y L. Tissue cells feel and respond to the stiffness of their substrate [J]. Science,2005,310(5751):1139-1143. doi: 10.1126/science.1116995 [8] ENGLER A J, SEN S, SWEENEY H L, DISCHER D E. Matrix elasticity directs stem cell lineage specification [J]. Cell,2006,126(4):677-689. doi: 10.1016/j.cell.2006.06.044 [9] DISCHER D E, MOONEY D J, ZANDSTRA P W. Growth factors, matrices, and forces combine and control stem cells [J]. Science,2009,324(5935):1673-1677. doi: 10.1126/science.1171643 [10] KOPECEK J. Hydrogels: From soft contact lenses and implants to self-assembled nanomaterials [J]. Journal of Polymer Science Part A:Polymer Chemistry,2009,47(22):5929-5946. doi: 10.1002/pola.23607 [11] BOATENG J S, MATTHEWS K H, STEVENS H N E, ECCLESTON G M. Wound healing dressings and drug delivery systems: A review [J]. Journal of Pharmaceutical Sciences,2008,97(8):2892-2923. doi: 10.1002/jps.21210 [12] KAMOUN E A, KENAWY E R S, CHEN X. A review on polymeric hydrogel membranes for wound dressing applications: PVA-based hydrogel dressings [J]. Journal of Advanced Research,2017,8(3):217-233. doi: 10.1016/j.jare.2017.01.005 [13] DONG L, AGARWAL A K, BEEBE D J, JIANG H. Adaptive liquid microlenses activated by stimuli-responsive hydrogels [J]. Nature,2006,442(7102):551-554. doi: 10.1038/nature05024 [14] HOLTZ J H, ASHER S A. Polymerized colloidal crystal hydrogel films as intelligent chemical sensing materials [J]. Nature,1997,389(6653):829-832. doi: 10.1038/39834 [15] LIU X Y, TANG T C, THAM E, YUK H, LIN S T, LU T K, ZHAO X H. Stretchable living materials and devices with hydrogel-elastomer hybrids hosting programmed cells [J]. Proceedings of the National Academy of Sciences of the United States of America,2017,114(9):2200-2205. doi: 10.1073/pnas.1618307114 [16] KIM Y S, LIU M J, ISHIDA Y, EBINA Y, OSADA M, SASAKI T, HIKIMA T, TAKATA M, AIDA T. Thermoresponsive actuation enabled by permittivity switching in an electrostatically anisotropic hydrogel [J]. Nature Materials,2015,14(10):1002-1007. doi: 10.1038/nmat4363 [17] YUK H, LIN S T, MA C, TAKAFFOLI M, FANG N X, ZHAO X H. Hydraulic hydrogel actuators and robots optically and sonically camouflaged in water [J]. Nature Communications,2017,8:14230. doi: 10.1038/ncomms14230 [18] LI T F, LI G R, LIANG Y M, CHENG T Y, DAI J, YANG X X, LIU B Y, ZENG Z D, HUANG Z L, LUO Y W, XIE T, YANG W. Fast-moving soft electronic fish [J]. Science Advances,2017,3(4):e1602045. doi: 10.1126/sciadv.1602045 [19] LIN X, ZHAO X, XU C, WANG L, XIA Y. Progress in the mechanical enhancement of hydrogels: Fabrication strategies and underlying mechanisms [J]. Journal of Polymer Science,2022,60(17):2525-2542. doi: 10.1002/pol.20220154 [20] ZHAO X H, CHEN X Y, YUK H, LIN S T, LIU X Y, PARADA G. Soft materials by design: Unconventional polymer networks give extreme properties [J]. Chemical Reviews,2021,121(8):4309-4372. doi: 10.1021/acs.chemrev.0c01088 [21] BONN D, KELLAY H, PROCHNOW M, BEN-DJEMIAA K, MEUNIER J. Delayed fracture of an inhomogeneous soft solid [J]. Science,1998,280(5361):265-267. doi: 10.1126/science.280.5361.265 [22] LAKE G L, THOMAS A G. The strength of highly elastic materials [J]. Proceedings of the Poyal Society London,1967,300(1460):108-119. [23] STOK K, OLOYEDE A. Conceptual fracture parameters for articular cartilage [J]. Clin Biomech (Bristol, Avon),2007,22(6):725-735. doi: 10.1016/j.clinbiomech.2007.03.005 [24] GONG J P. Why are double network hydrogels so tough? [J]. Soft Matter,2010,6(12):2583-2590. doi: 10.1039/b924290b [25] KAMATA H, AKAGI Y, KAYASUGA-KARIYA Y, CHUNG U I, SAKAI T. "Nonswellable" hydrogel without mechanical hysteresis [J]. Science,2014,343(6173):873-875. doi: 10.1126/science.1247811 [26] SAKAI T, MATSUNAGA T, YAMAMOTO Y, ITO C, YOSHIDA R, SUZUKI S, SASAKI N, SHIBAYAMA M, CHUNG U I. Design and fabrication of a high-strength hydrogel with ideally homogeneous network structure from tetrahedron-like macromonomers [J]. Macromolecules,2008,41(14):5379-5384. doi: 10.1021/ma800476x [27] OKUMURA Y, ITO K. The polyrotaxane gel: A topological gel by figure-of-eight cross-links [J]. Advanced Materials,2001,13(7):485-487. doi: 10.1002/1521-4095(200104)13:7<485::AID-ADMA485>3.0.CO;2-T [28] CRETON C. 50th Anniversary perspective: Networks and gels: Soft but dynamic and tough [J]. Macromolecules,2017,50(21):8297-8316. doi: 10.1021/acs.macromol.7b01698 [29] GONG J P, KATSUYAMA Y, KUROKAWA T, OSADA Y. Double-network hydrogels with extremely high mechanical strength [J]. Advanced Materials,2003,15(14):1155-1158. doi: 10.1002/adma.200304907 [30] TANAKA Y, KUWABARA R, NA Y H, KUROKAWA T, GONG J P, OSADA Y. Determination of fracture energy of high strength double network hydrogels [J]. Journal of Physical Chemistry B,2005,109(23):11559-11562. doi: 10.1021/jp0500790 [31] NA Y H, TANAKA Y, KAWAUCHI Y, FURUKAWA H, SUMIYOSHI T, GONG J P, OSADA Y. Necking phenomenon of double-network gels [J]. Macromolecules,2006,39(14):4641-4645. doi: 10.1021/ma060568d [32] HUANG M, FURUKAWA H, TANAKA Y, NAKAJIMA T, OSADA Y, GONG J P. Importance of entanglement between first and second components in high-strength double network gels [J]. Macromolecules,2007,40(18):6658-6664. doi: 10.1021/ma062482q [33] TSUKESHIBA H, HUANG M, NA Y H, KUROKAWA T, KUWABARA R, TANAKA Y, FURUKAWA H, OSADA Y, GONG J P. Effect of polymer entanglement on the toughening of double network hydrogels [J]. Journal of Physical Chemistry B,2005,109(34):16304-16309. doi: 10.1021/jp052419n [34] NAKAJIMA T, FURUKAWA H, TANAKA Y, KUROKAWA T, OSADA Y, GONG J P. True chemical structure of double network hydrogels [J]. Macromolecules,2009,42(6):2184-2189. doi: 10.1021/ma802148p [35] NA Y H, KUROKAWA T, KATSUYAMA Y, TSUKESHIBA H, GONG J P, OSADA Y, OKABE S, KARINO T, SHIBAYAMA M. Structural characteristics of double network gels with extremely high mechanical strength [J]. Macromolecules,2004,37(14):5370-5374. doi: 10.1021/ma049506i [36] LONG R, HUI C Y. Fracture toughness of hydrogels: Measurement and interpretation [J]. Soft Matter,2016,12(39):8069-8086. doi: 10.1039/C6SM01694D [37] LONG R, HUI C Y, GONG J P, BOUCHBINDER E. The fracture of highly deformable soft materials: A tale of two length scales [J]. Annual Review of Condensed Matter Physics,2021,12(1):71-94. doi: 10.1146/annurev-conmatphys-042020-023937 [38] ZHAO X H. Designing toughness and strength for soft materials [J]. Proceedings of the National Academy of Sciences of the United States of America,2017,114(31):8138-8140. doi: 10.1073/pnas.1710942114 [39] LAKE G J, LINDLEY P B. Cut growth and fatigue of rubbers: II. Experiments on a noncrystallizing rubber [J]. Journal of Applied Polymer Science,1964,8(2):707-721. doi: 10.1002/app.1964.070080212 [40] LAKE G J, LINDLEY P B. The mechanical fatigue limit for rubber [J]. Journal of Applied Polymer Science,1965,9(4):1233-1251. doi: 10.1002/app.1965.070090405 [41] SUN J Y, ZHAO X H, ILLEPERUMA W R K, CHAUDHURI O, OH K H, MOONEY D J, VLASSAK J J, SUO Z G. Highly stretchable and tough hydrogels [J]. Nature,2012,489(7414):133-136. doi: 10.1038/nature11409 [42] DUCROT E, CHEN Y L, BULTERS M, SIJBESMA R P, CRETON C. Toughening elastomers with sacrificial bonds and watching them break [J]. Science,2014,344(6180):186-189. doi: 10.1126/science.1248494 [43] GONG J P. Materials both tough and soft [J]. Science,2014,344(6180):161-162. doi: 10.1126/science.1252389 [44] FAROOQ U, TEUWEN J, DRANSFELD C. Toughening of epoxy systems with interpenetrating polymer network (IPN): A review [J]. Polymers,2020,12(9):1908. doi: 10.3390/polym12091908 [45] NAKAJIMA T, KUROKAWA T, AHMED S, WU W L, GONG J P. Characterization of internal fracture process of double network hydrogels under uniaxial elongation [J]. Soft Matter,2013,9(6):1955-1966. doi: 10.1039/C2SM27232F [46] MATSUDA T, NAKAJIMA T, FUKUDA Y, HONG W, SAKAI T, KUROKAWA T, CHUNG U, GONG J P. Yielding criteria of double network hydrogels [J]. Macromolecules,2016,49(5):1865-1872. doi: 10.1021/acs.macromol.5b02592 [47] WEBBER R E, CRETON C, BROWN H R, GONG J P. Large strain hysteresis and mullins effect of tough double-network hydrogels [J]. Macromolecules,2007,40(8):2919-2927. doi: 10.1021/ma062924y [48] FURUKAWA H, KUWABARA R, TANAKA Y, KUROKAWA T, NA Y H, OSADA Y, GONG J P. Tear velocity dependence of high-strength double network gels in comparison with fast and slow relaxation modes observed by scanning microscopic light scattering [J]. Macromolecules,2008,41(19):7173-7178. doi: 10.1021/ma800821j [49] BROWN H R. A model of the fracture of double network gels [J]. Macromolecules,2007,40(10):3815-3818. doi: 10.1021/ma062642y [50] TANAKA Y. A local damage model for anomalous high toughness of double-network gels [J]. Epl,2007,78(5):56005. doi: 10.1209/0295-5075/78/56005 [51] MATSUDA T, KAWAKAMI R, NAKAJIMA T, GONG J P. Crack tip field of a double-network gel: Visualization of covalent bond scission through mechanoradical polymerization [J]. Macromolecules,2020,53(20):8787-8795. doi: 10.1021/acs.macromol.0c01485 [52] ZHANG Y, FUKAO K, MATSUDA T, NAKAJIMA T, TSUNODA K, KUROKAWA T, GONG J P. Unique crack propagation of double network hydrogels under high stretch [J]. Extreme Mechanics Letters,2022,51:101588. doi: 10.1016/j.eml.2021.101588 [53] MATSUDA T, KAWAKAMI R, NAMBA R, NAKAJIMA T, GONG J P. Mechanoresponsive self-growing hydrogels inspired by muscle training [J]. Science,2019,363(6426):504-508. doi: 10.1126/science.aau9533 [54] MU Q, CUI K, WANG Z J, MATSUDA T, CUI W, KATO H, NAMIKI S, YAMAZAKI T, FRAUENLOB M, NONOYAMA T, TSUDA M, TANAKA S, NAKAJIMA T, GONG J P. Force-triggered rapid microstructure growth on hydrogel surface for on-demand functions [J]. Nat Commun,2022,13:6213. doi: 10.1038/s41467-022-34044-8 [55] KRISHNAKUMAR B, SANKA R V S P, BINDER W H, PARTHASARTHY V, RANA S, KARAK N. Vitrimers: Associative dynamic covalent adaptive networks in thermoset polymers [J]. Chemical Engineering Journal,2020,385:123820. doi: 10.1016/j.cej.2019.123820 [56] SUN T L, KUROKAWA T, KURODA S, IHSAN A B, AKASAKI T, SATO K, HAQUE M A, NAKAJIMA T, GONG J P. Physical hydrogels composed of polyampholytes demonstrate high toughness and viscoelasticity [J]. Nature Materials,2013,12(10):932-937. doi: 10.1038/nmat3713 [57] SUN T L, LUO F, HONG W, CUI K P, HUANG Y W, ZHANG H J, KING D R, KUROKAWA T, NAKAJIMA T, GONG J P. Bulk energy dissipation mechanism for the fracture of tough and self-healing hydrogels [J]. Macromolecules,2017,50(7):2923-2931. doi: 10.1021/acs.macromol.7b00162 [58] CUI K P, SUN T L, LIANG X B, NAKAJIMA K, YE Y N, CHEN L, KUROKAWA T, GONG J P. Multiscale energy dissipation mechanism in tough and self-healing hydrogels [J]. Physical Review Letters,2018,121(18):185501. doi: 10.1103/PhysRevLett.121.185501 [59] CUI K P, YE Y N, SUN T L, CHEN L, LI X Y, KUROKAWA T, NAKAJIMA T, NONOYAMA T, GONG J P. Effect of structure heterogeneity on mechanical performance of physical polyampholytes hydrogels [J]. Macromolecules,2019,52(19):7369-7378. doi: 10.1021/acs.macromol.9b01676 [60] CUI K P, YE Y N, SUN T L, YU C T, LI X Y, KUROKAWA T, GONG J P. Phase separation behavior in tough and self-healing polyampholyte hydrogels [J]. Macromolecules,2020,53(13):5116-5126. doi: 10.1021/acs.macromol.0c00577 [61] CUI K P, YE Y N, YU C T, LI X Y, KUROKAWA T, GONG J P. Stress relaxation and underlying structure evolution in tough and self-healing hydrogels [J]. Acs Macro Letters,2020,9(11):1582-1589. doi: 10.1021/acsmacrolett.0c00600 [62] LI X Y, CUI K P, SUN T L, MENG L P, YU C T, LI L B, CRETON C, KUROKAWA T, GONG J P. Mesoscale bicontinuous networks in self-healing hydrogels delay fatigue fracture [J]. Proceedings of the National Academy of Sciences of the United States of America,2020,117(14):7606-7612. doi: 10.1073/pnas.2000189117 [63] WILLIAMS M L, LANDEL R F, FERRY J D. The temperature dependence of relaxation mechanisms in amorphous polymers and other glass-forming liquids [J]. Journal of the American Chemical Society,1955,77(14):3701-3707. doi: 10.1021/ja01619a008 [64] PERSSON B N J, ALBOHR O, HEINRICH G, UEBA H. Crack propagation in rubber-like materials [J]. Journal of Physics: Condensed Matter,2005,17(44):R1071-R1142. doi: 10.1088/0953-8984/17/44/R01 [65] PERSSON B N J, BRENER E A. Crack propagation in viscoelastic solids [J]. Physical Review E,2005,71(3):036123. doi: 10.1103/PhysRevE.71.036123 [66] DEGENNES P G. Soft adhesives [J]. Langmuir,1996,12(19):4497-4500. doi: 10.1021/la950886y [67] LI J Y, ILLEPERUMA W B K, SUO Z G, VLASSAK J J. Hybrid hydrogels with extremely high stiffness and toughness [J]. Acs Macro Letters,2014,3(6):520-523. doi: 10.1021/mz5002355 [68] ROWLEY J A, MADLAMBAYAN G, MOONEY D J. Alginate hydrogels as synthetic extracellular matrix materials [J]. Biomaterials,1999,20(1):45-53. doi: 10.1016/S0142-9612(98)00107-0 [69] LIN S T, LONDONO C D, ZHENG D C, ZHAO X H. An extreme toughening mechanism for soft materials [J]. Soft Matter,2022,18(31):5742-5749. doi: 10.1039/D2SM00609J [70] ZHENG D C, LIN S T, NI J H, ZHAO X H. Fracture and fatigue of entangled and unentangled polymer networks [J]. Extreme Mechanics Letters,2022,51:101608. doi: 10.1016/j.eml.2022.101608 [71] NORIOKA C, INAMOTO Y, HAJIME C, KAWAMURA A, MIYATA T. A universal method to easily design tough and stretchable hydrogels [J]. Npg Asia Materials,2021,13(1):34. doi: 10.1038/s41427-021-00302-2 [72] KIM J, ZHANG G G, SHI M X, SUO Z G. Fracture, fatigue, and friction of polymers in which entanglements greatly outnumber cross-links [J]. Science,2021,374(6564):212-216. doi: 10.1126/science.abg6320 [73] NIAN G D, KIM J, BAO X Y, SUO Z G. Making highly elastic and tough hydrogels from doughs [J]. Advanced Materials,2022,34(50):2206577. doi: 10.1002/adma.202206577 [74] SLOOTMAN J, WALTZ V, YEH C J, BAUMANN C, GOSTL R, COMTET J, CRETON C. Quantifying rate- and temperature-dependent molecular damage in elastomer fracture [J]. Physical Review X,2020,10(4):041045. doi: 10.1103/PhysRevX.10.041045 [75] BOSNJAK N, SILBERSTEIN M N. Pathways to tough yet soft materials [J]. Science,2021,374(6564):150-151. doi: 10.1126/science.abl6358 [76] PEPPAS N A, HILT J Z, KHADEMHOSSEINI A, LANGER R. Hydrogels in biology and medicine: From molecular principles to bionanotechnology [J]. Advanced Materials,2006,18(11):1345-1360. doi: 10.1002/adma.200501612 [77] KER R F. The design of soft collagenous load-bearing tissues [J]. Journal of Experimental Biology,1999,202(23):3315-3324. doi: 10.1242/jeb.202.23.3315 [78] CALVERT P. Hydrogels for soft machines [J]. Advanced Materials,2009,21(7):743-756. doi: 10.1002/adma.200800534 [79] PRABHAKAR C G, BABU K A, KATARAKI P S, REDDY S. A review on natural fibers and mechanical properties of banyan and banana fibers composites [J]. Materials Today: Proceedings,2022,54:348-358. doi: 10.1016/j.matpr.2021.09.300 [80] KING D R, SUN T L, HUANG Y W, KUROKAWA T, NONOYAMA T, CROSBY A J, GONG J P. Extremely tough composites from fabric reinforced polyampholyte hydrogels [J]. Materials Horizons,2015,2(6):584-591. doi: 10.1039/C5MH00127G [81] HUANG Y W, KING D R, SUN T L, NONOYAMA T, KUROKAWA T, NAKAJIMA T, GONG J P. Energy-dissipative matrices enable synergistic toughening in fiber reinforced soft composites [J]. Advanced Functional Materials,2017,27(9):1605350. doi: 10.1002/adfm.201605350 [82] HUANG Y, KING D R, CUI W, SUN T L, GUO H, KUROKAWA T, BROWN H R, HUI C Y, GONG J P. Superior fracture resistance of fiber reinforced polyampholyte hydrogels achieved by extraordinarily large energy-dissipative process zones [J]. Journal of Materials Chemistry A,2019,7(22):13431-13440. doi: 10.1039/C9TA02326G [83] ROY C K, GUO H L, SUN T L, BIN IHSAN A, KUROKAWA T, TAKAHATA M, NONOYAMA T, NAKAJIMA T, GONG J P. Self-adjustable adhesion of polyampholyte hydrogels [J]. Advanced Materials,2015,27(45):7344-7348. doi: 10.1002/adma.201504059 [84] CHEN C, WANG Z J, SUO Z G. Flaw sensitivity of highly stretchable materials [J]. Extreme Mechanics Letters,2017,10:50-57. doi: 10.1016/j.eml.2016.10.002 [85] THOMAS A G. Rupture of rubber: II. The strain concentration at an incision [J]. Journal of Polymer Science,1955,18(88):177-188. doi: 10.1002/pol.1955.120188802 [86] VOLOKH K Y, TRAPPER P. Fracture toughness from the standpoint of softening hyperelasticity [J]. Journal of the Mechanics and Physics of Solids,2008,56(7):2459-2472. doi: 10.1016/j.jmps.2008.02.009 [87] HUI C Y, LIU Z Z, PHOENIX S L. Size effect on elastic stress concentrations in unidirectional fiber reinforced soft composites [J]. Extreme Mechanics Letters,2019,33:100573. doi: 10.1016/j.eml.2019.100573 -
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