Stretchable alkaline quasi-solid-state electrolytes created by super-tough,fatigue-resistant and alkali-resistant multi-bond network hydrogels

Hydrogel-based quasi-solid-state electrolytes (Q-SSEs) swollen with electrolyte solutions are important components in stretchable supercapacitors and other wearable devices. This work fabricates a super-tough, fatigue-resistant, and alkali-resistant multi-bond network (MBN) hydrogel aiming to be an alkaline Q-SSE. To synthesize the hydrogel, a 2-ureido-4[1H]-pyrimidone (UPy) motif is introduced into a poly(acrylic acid) polymer chain. The obtained MBN hydrogels with 75 wt% water content exhibit tensile strength as high as 2.47 MPa, which is enabled by the large energy dissipation ability originated from the dissociation of UPy dimers due to their high bond association energy. Owing to the high dimerization constant of UPy motifs, the dissociated UPy motifs are able to partially re-associate soon after being released from external forces, resulting in excellent fatigue-resistance. More importantly, the MBN hydrogels exhibit excellent alkali-resistance ability. The UPyGel-10 swollen with 1 mol/L KOH display a tensile strength as high as ～1.0 MPa with elongation at break of ～550%. At the same time, they show ionic conductivity of ～17 mS/cm, which do not decline even when the hydrogels are stretched to 500% strain. The excellent mechanical property and ionic conductivity of the present hydrogels demonstrate potential application as a stretchable alkaline Q-SSE.     

Multi-bond network hydrogels with robust mechanical and self-healable properties

Multi-bond network(MBN) which contains a single network with hierarchical cross-links is a suggested way to fabricate robust hydrogels. In order to reveal the roles of different cross-links with hierarchical bond energy in the MBN, here we fabricate poly(acrylic acid) physical hydrogels with dual bond network composed of ionic cross-links between carboxylFe3+ interactions and hydrogen bonds, and compare these dually cross-linked hydrogels with singly and ternarily cross-linked hydrogels. Simple models are employed to predict the tensile property, and the results confirm that the multi-bond network with hierarchical distribution in the bond energy of cross-links endows hydrogel with effective energy-dissipating mechanism. Moreover, the dually cross-linked MBN gels exhibit excellent mechanical properties(tensile strength up to 500 k Pa, elongation at break ~ 2400%) and complete self-healing after being kept at 50 °C for 48 h. The factors on promoting self-healing are deeply explored and the dynamic multi-bonds are regarded to trigger the self-healing along with the mutual diffusion of long polymer chains and ferric ions.     

强韧抗溶胀水凝胶的简单构筑及性能

以聚乙烯醇(PVA)和壳聚糖(CS)为原料, 采用循环冻融法制备了前驱体水凝胶(PVA-CS), 并经过浸泡氯化钠溶液和透析后处理构筑了强韧抗溶胀复合水凝胶(PVA-CS-6.16-30). 采用扫描电子显微镜(SEM)、 傅里叶变换红外光谱仪(FTIR)、 X射线衍射分析仪(XRD)、 差示扫描量热分析仪(DSC)及流变仪表征了两种水凝胶的微观结构, 采用拉力机测试了其机械性能. 结果表明: 由于结晶微区、 氢键及链缠结等协同交联作用, PVA-CS-6.16-30具备高效能量耗散机制. 与前驱体PVA-CS相比, PVA-CS-6.16-30的交联密度由7.69×10^?4 mol/cm³增加至9.97×10^?4 mol/cm³, 自由水含量由62.8%降低至52.6%, 网络尺寸由6.11 nm降低至5.21 nm, 凝胶分数由58.6%增加至86.8%, PVA结晶度由14.8%增加至17.2%, 其抗拉强度、 断裂伸长率、 韧性及抗压强度分别为2.9 MPa, 229%, 3.3 MJ/m³和7.6 MPa. 此外, 该复合水凝胶还具有优异的耐溶胀与抗蠕变性能. 在37 ℃的PBS缓冲溶液中浸泡7 d后, 其抗拉和抗压强度分别高达2.8和7.5 MPa, 优于常见水凝胶. 商品化的原料、 简单的构筑方法及优异的综合性能有望推动水凝胶在组织工程和生物医疗领域的应用.     

基于金属配位键的自修复、 可重塑聚丁二烯橡胶的合成及性能

橡胶材料通常因经过硫化及补强等工艺处理而呈现出热固性, 因而难以被回收处理, 容易造成严重的资源浪费和环境污染. 本文通过在聚丁二烯上修饰羧酸基团, 再加入锌离子(Zn²⁺)与羧酸配位, 制备了基于金属配位键交联的自修复橡胶(PB-COOH/Zn²⁺). 该橡胶具有良好的机械性能和优秀的自修复及重塑性能, 在70 ℃下修复3 h, 其韧性可以恢复到初始强度, 修复效率可达100%. PB-COOH/Zn²⁺较高的聚合物链段运动能力及配位键交联网络良好的动态性不仅赋予其优异的修复性能, 还使得其在较温和的条件下可以进行多次重塑, 在70 ℃及5 MPa的条件下重塑3次仍能保持原有的机械性能. 此外, 通过在PB-COOH/Zn²⁺中掺杂适量的碳纳米管, 不仅增强了其机械性能, 还使其具备了电致修复及传感能力, 扩宽了PB-COOH/Zn²⁺作为环境友好型材料的应用前景.     

Self‐Healing Gelatin Hydrogels Cross‐Linked by Combining Multiple Hydrogen Bonding and Ionic Coordination

Self‐healing hydrogels have been studied by many researchers via multiple cross‐linking approaches including physical and chemical interactions. It is an interesting project in multifunctional hydrogel exploration that a water soluble polymer matrix is cross‐linked by combining the ionic coordination and the multiple hydrogen bonds to fabricate self‐healing hydrogels with injectable property. This study introduces a general procedure of preparing the hydrogels (termed gelatin‐UPy‐Fe) cross‐linked by both ionic coordination of Fe³⁺ and carboxyl group from the gelatin and the quadruple hydrogen bonding interaction from the ureido‐pyrimidinone (UPy) dimers. The gelatin‐UPy‐Fe hydrogels possess an excellent self‐healing property. The effects of the ionic coordination of Fe³⁺ and quadruple hydrogen bonding of UPy on the formation and mechanical behavior of the prepared hydrogels are investigated. In vitro drug release of the gelatin‐UPy‐Fe hydrogels is also observed, giving an intriguing glimpse into possible biological applications.

     

石墨烯诱导水凝胶成核的高强韧人造蛛丝

天然蜘蛛丝是由β-sheet交联的蛛丝蛋白溶剂流入S-型导管后经牵引拉伸形成,它显示了高强度与高韧性的完美结合。其优异的力学性质主要源于它的多级结构：交联、线性排列的纳米组装体以及核壳结构。受此启发,我们合成了一种交联的水凝胶,通过牵引拉丝的方法,制备了交联的、含有取向排列的纳米组装体结构以及核壳结构的凝胶纤维,并通过少量引入二维纳米材料—氧化石墨烯(0.01%),进一步调控纳米组装体的取向和尺寸,实现了蜘蛛丝般优异的力学性能(断裂强度560 MPa,断裂韧性200 MJ·m^–3,缓冲能94%)。这种纤维可以用于高速下落物体的能量耗散和降低冲击力。     

A Well-defined Hierarchical Hydrogen Bonding Strategy to Polyureas with Simultaneously Improved Strength and Toughness

A well-defined quadruple hydrogen bonding strategy involving dimerization of 2-ureido-4[1H]-pyrimidone(UPy) units is innovatively designed to prepare polyureas with high overall mechanical properties. Three polyureas containing different amounts of UPy units were synthesized by replacing a portion of isophorone diisocyanate(IPDI) with a UPy-derived diisocyanate. The formation of quadruple hydrogen bonds in hard segments via UPy dimers was confirmed by nuclear magnetic resonance(NMR) and Fourier transform infrared spectroscopy(FTIR). The mechanical properties of the polyureas were evaluated by uniaxial tensile testing. Compared to the polyurea without UPy units, remarkable improvements in Young's modulus, tensile strength, and toughness were simultaneously achieved when UPy units were incorporated. The mechanism behind the strong strengthening effect rooted in the stronger intermolecular forces among hard segments brought by the quadruple hydrogen bonds, which were stronger than the inherent bidentate and monodentate hydrogen bonds among urea groups, and the slower soft segmental dynamics reaveled by both increased Tg and relaxation time of the soft segments. The mechanism behind the strong toughening effect was ascribed to more effective energy dissipation brought by the quadruple hydrogen bonds that served as stronger sacrificial bonds upon deformation. This work may offer new insight into the design of polyurea elastomers with comprehensively improved mechanical properties.     

Preparation and Characterization of Attractive Poly(amino acid)Hydrogels Based on 2-Ureido-4[1H]-pyrimidinone

Self-healing hydrogels with the shear-thinning property are novel injectable materials and are superior to traditional injectable hydrogels.The self-healing hydrogels based on 2-ureido-4[1 H]-pyrimidinone(UPy)have recently received extensive attention due to their dynamic reversibility of UPy dimerization.However,generally,UPy-based self-healing hydrogels exhibit poor stability,cannot degrade in vivo and can hardly be excreted from the body,which considerably limit their bio-application.Here,using poly(l-glutamic acid)(PLGA)as biodegradable matrix,branchingα-hydroxy-ω-amino poly(ethylene oxide)(HAPEO)as bridging molecule to introduce UPy,and ethyl acrylate polyethylene glycol(MAPEG)to introduce double bond,the hydrogel precursors(PMHU)are prepared.A library of the self-healing hydrogels has been achieved with well self-healable and shear-thinning properties.With the increase of MAPEG grafting ratio,the storage modulus of the self-healing hydrogels decreases.The self-healing hydrogels are stable in solution only for 6 h,hard to meet the requirements of tissue regeneration.Consequently,ultraviolet(UV)photo-crosslinking is involved to obtain the dual crosslinking hydrogels with enhanced mechanical properties and stability.When MAPEG grafting ratio is 35.5%,the dual crosslinking hydrogels can maintain the shape in phosphate-buffered saline solution(PBS)for at least 8 days.Loading with adipose-derived stem cell spheroids,the self-healing hydrogels are injected and self-heal to a whole,and then they are crosslinked in situ via UV-irradiation,obtaining the dual crosslinking hydrogels/cell spheroids complex with cell viability of 86.7%±6.0%,which demonstrates excellent injectability,subcutaneous gelatinization,and biocompatibility of hydrogels as cell carriers.The novel PMHU hydrogels crosslinked by quadruple hydrogen bonding and then dual photo-crosslinking of double bond are expected to be applied for minimal invasive surgery or therapies in tissue engineering.     

耐高温核/壳结构TiO2/SiO2复合气凝胶的制备及其光催化性能

以钛酸四丁酯为源, 采用苯胺-丙酮原位生成水溶胶-凝胶法, 在乙醇超临界干燥过程中用部分水解的钛醇盐和硅醇盐对TiO₂凝胶进行超临界修饰制备了具有核/壳纳米结构的块体TiO₂/SiO₂复合气凝胶. 制备的复合气凝胶具有优异的机械性能, 其杨氏模量可达4.5 MPa. 复合气凝胶同时具有极好的高温热稳定性. 经过1000 ℃热处理后, 线性收缩由纯TiO₂气凝胶的31%降至复合气凝胶的10%, 且比表面积由纯TiO₂气凝胶的31 m²·g^-1提升至复合气凝胶的143 m²·g^-1. 此外, 该复合气凝胶经1000 ℃热处理后具有优异的光催化降解亚甲基蓝的性能. 其优异的光催化性能得益于TiO₂/SiO₂复合气凝胶1000 ℃处理后高的比表面积和小的颗粒尺寸. 优良的耐热性能、力学性能和光催化性能使获得的具有核/壳纳米结构的TiO₂/SiO₂复合气凝胶在光催化领域具有良好的应用前景.     

Toughening hydrogels by immersing with oppositely charged polymers

A very simple yet novel strategy to significantly enhance the mechanical properties of hydrogels is reported. Poly(acrylic acid) (PAA) hydrogels with aligned macroporous channels are immersed in the aqueous solutions of poly(dimethyl diallyl ammonium chloride) (PDMDAAC). Strong electrostatic interactions are formed between the anionic PAA and cationic PDMDAAC chains. In the resultant PAA/PDMDAAC hybrid hydrogels, the mass ratio of PDMDAAC to PAA is about 0.2 and PDMDAAC is uniformly distributed throughout the gels. The mechanical properties of the formed hybrid hydrogels are largely enhanced in comparison with the original PAA hydrogels. The hybrid hydrogels exhibit high tensile strengths (0.38–1.73 MPa), elastic moduli (0.21–1.59 MPa) and toughness (up to 3.0 MJ/m³), about several to more than 10 times those of the corresponding PAA hydrogels. In addition, the PAA/PDMDAAC hydrogels also show excellent and very rapid shape recovery ability in both air and deionized water. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2432–2441     

Porous Silicon Carbide/Carbon Composite Microspherules for Methane Storage

Porous silicon carbide/carbon(SiC/C)microspherules were prepared by the controlled heating treatment of polymer and silica hybrid precursors over 1000℃in Ar/H_2 stream.The resultant SiC/C composite shows improved physical properties such as excellent mechanical strength,regular physical form, and high packing density.Such improvement overcomes the main inherent problems encountered when using activated carbons as absorbents without sacrificing porosity properties.N_2 sorption analysis shows that the SiC/C composite has a BET surface area of 1793 m~2/g and a pore volume of 0.92 ml/g.Methane adsorption isotherm is determined by the conventional volumetric method at 25℃and up to 7.0 MPa.On volumetric basis,the SiC/C composite microspherules show methane storage of 145(V/V)at 3.5 MPa and 25℃.The combination of excellent physical properties and porosity properties in this SiC/C composite lends a great possibility to develop a competitive storage system for natural gas.     

Robust self-healing waterborne polyurethane coatings via dynamic covalent Diels-Alder bonds for corrosion protection

For waterborne polyurethanes (PUs), balancing robust mechanical performances and excellent self-healing ability is a great challenge. Here, we show that this goal can be achieved by a rational tuning of the PU chemistry. In particular, we synthesized an anionic self-healing waterborne PU using acetone process, in which 2,2-bis(hydroxymethyl)propionic acid (DMPA) serves as inner emulsifier, thermally dynamic Diels-Alder bonds act as healing motifs and hexamethylene diisocyanate trimer is the crosslinker. The mechanical performance can be tuned by increasing DMPA concentration due to the gradually increased hard segment contents and ionic interactions. The tensile stress and elongation at break of films containing 5.6 wt% of DMPA are 24.9 MPa and 911.9%, respectively. Moreover, dynamic reversible Diels-Alder bonds located in main chains and cross-linking points ensure excellent self-repairing capability. Upon mechanical damage, the tensile stress can be restored to 95% of its initial value. Electrochemical impedance spectroscopy also points out an outstanding barrier ability and excellent corrosion protection performance of the coatings, which can be recovered even after serious damages.     

Tough polyion complex hydrogel films of natural polysaccharides

The developments of tough hydrogels in recent years have greatly expanded the applications of hydrogels as structural materials. However, most of the tough hydrogels are made of synthetic polymers. To develop biopolymer-based tough hydrogels has both fundamental and practical significances. Here we report a series of polysaccharides-based tough hydrogel films prepared by polyion complexation and solvent evaporation of chondroitin sulfate(CS) and protonated chitosan(CHT) solutions with different weight ratios. The obtained CS/CHT gel films with thickness of 40-80 μm and water content of 66 wt%-81 wt% possess excellent mechanical properties, with tensile breaking stress and breaking strain being 0.4-3 MPa and 160%-320%, respectively. We found that in the mixture solutions there are large amounts of excess CHT in terms of charges; after swelling the films in water, the acetic acid, which is used to protonate the amino groups of CHT, diffuses out of the gel matrix, enhancing the intermolecular interactions between CHT molecules and thus improving the mechanical properties of gel films, besides the ionic bonds between CS and CHT. Antimicrobial tests also showed that the gel films with low weight ratio of CS to CHT, corresponding to the case with excess CHT, have evident antimicrobial effect. These CS/CHT gel films with good mechanical properties and antimicrobial effect should extend the applications of hydrogels in biomedical fields.     

Strong and Tough TPU Fibers with Orientedly Aligned CNTs Reinforced by Amorphous ZrO2

High strength and high toughness are vital for fibers' engineering applications, but are hard to simultaneously achieve. Herein, we synthesize a carbon nanotube(CNT)-thermoplastic polyurethanes(TPU) fiber reinforced by an amorphous ZrO₂ layer through the wet-spinning method. The amorphous ZrO₂ layer is in-situ grown on the surface of CNT and the hybrid nanowires are orientedly aligned with TPU to form the ternary fiber. The fiber possesses an excellent combination of high strength(84.6 MPa) and toughness(126.7 MJ/m³), which is outstanding when compared with previously reported CNT-TPU fibers. The pull-out of nanowires attributed to the oriented alignment structure and the enhanced interface and restriction of deformation obtained from the amorphous ZrO₂ layer are considered as the primary strengthening and toughening mechanisms. We anticipate that our fiber synthesis strategy gives a new path to design strong and tough fibers.     

Polyprotein Cross-linked Hydrogels with High Stretchability,Fracture Toughness and Low Hysteresis

It is challenging to realize both high fracture toughness and low hysteresis perfectly in synthetic systems, which restricts the use of stretchable hydrogels in load-bearing applications. Recently, by imbedding the folded polyprotein cross-linker in a percolating random coiled network, Cao et al. demonstrated a highly stretchable hydrogel, which shows low hysteresis(<5%) but achieves high fracture toughness(ca. 900 J/m²). Moreover, the hydrogel shows outstanding anti-fatigue properties with a fatigue fracture threshold of 126 J/m². The unique network structure breaks the hysteresis-toughness correlation that is usually reported in stretchable and tough hydrogels. This work has been published in the Nature Communications and can be reached at https://doi.org/10.1038/s41467-020-17877-z.     

磷杂菲改性腰果酚多元醇的合成及阻燃聚氨酯硬泡性能

采用生物质原料腰果酚和9,10-二氢-9-氧杂-10-膦杂菲-10-氧化物(DOPO)为原料, 合成了一种磷杂菲改性腰果酚多元醇(P-Cardanol-Polyol), 并利用核磁共振氢谱和磷谱对其结构进行了表征. 利用P-Cardanol-Polyol对聚氨酯硬泡(RPUF)进行阻燃改性, 得到一系列阻燃聚氨酯硬泡. 考察了P-Cardanol-Polyol的用量对阻燃聚氨酯硬泡的形貌、 密度、 热导率、 压缩性能、 热稳定性以及阻燃性能的影响. 研究结果表明, P-Cardanol-Polyol对聚氨酯硬泡的密度影响可以忽略不计; 随着P-Cardanol-Polyol的加入, 阻燃聚氨酯硬泡的平均孔径逐渐减小, 热导率也逐渐降低. 未改性聚氨酯硬泡的最大热释放速率和总放热量分别为390 kW/m²和31.9 MJ/m², 阻燃聚氨酯硬泡则降低至340 kW/m²和24.6 MJ/m². 此外, 阻燃聚氨酯硬泡的压缩强度比未改性聚氨酯硬泡提升了约13%. 炭层分析结果表明, P-Cardanol-Polyol能够促进聚氨酯硬泡形成连续致密且具有良好抗热氧化性能的炭层, 有利于减少燃烧过程中可燃性气体的逸出, 从而提升阻燃性能.     

Mechanically tough and recoverable hydrogels via dual physical crosslinkings

Development of functional tough hydrogels with new network structures and energy dissipation mechanisms has great promise for many applications. Here, a new type of physical hydrogel crosslinked by hydrophobic association and hydrogen bonds was synthesized by a facile micellar copolymerization of hydrophobic methyl acrylate (MA) monomers and hydrophilic N-hydroxyethyl acrylamide (HEAA) monomers in the presence of Tween80 micelles. Strong hydrophobic association between inner MA and Tween80 and hydrogen bonds between external polyHEAA and Tween80 provide two distinct crosslinkers to construct mechanically tough and recoverable network. Mechanical properties of polyHEAA-MA@Tween80 hydrogels strongly depended on network components (HEAA, MA; Tween80 concentrations). At optimal conditions, the hydrogels can achieve fracture stress of 700 kPa, fracture strain of 1687 mm/mm, elastic modulus of 195 kPa, and tearing energy of 1598 J/m². Due to the reversible nature of physical interactions, polyHEAA-MA@Tween80 hydrogels can achieve fast stiffness/toughness recovery of 60%/33% without any external stimuli and resting time at room temperature. This work demonstrates a new design strategy to fabricate a new a single-network hydrogel with high mechanical and self-recovery properties by incorporating both hydrophobic association and hydrogen bonds in the network, which may provide alternative viewpoint for the design of multifunctional tough hydrogels. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1294–1305     

层状纳米纤维素膜/PVA复合水凝胶的制备与力学性能研究

采用叠层复合与物理相分离的方法制备了层状纳米细菌纤维素(BC)膜/聚乙烯醇( PVA)复合水凝胶.研究了聚乙烯醇的质量百分数、BC膜的复合层数以及制备条件对复合水凝胶力学性能的影响;通过扫描电镜( SEM)观察比较了复合水凝胶中BC膜层与PVA界面结合情况.结果表明,复合水凝胶的力学性能与PVA的质量百分数和BC膜含水...     

Bentonite Reinforced Tough Composite Hydrogels as Potential Artificial Articular Cartilage

Novel tough composite hydrogels were prepared from inorganic bentonite(IB), polyvinyl alcohol(PVA) and polyethylene glycol(PEG) by means of a freeze-thaw technique, during which IB acted as multifunctional physically crosslinking junction and a filler to bridge the 3D network hydrogel; while the physical adsorption between IB and the polymer chains served as sacrificial bonds and increased the energy dissipation efficiency. The effects of different content of IB(w_IB) on the morphological, thermal, swelling, and mechanical properties of the hydrogels were investigated. It was found that the added IB promoted the material crosslinking and stability, and the mechanical properties of the hydrogels were significantly improved with increasing w_IB. The highest tensile stress of the hydrogel was achieved(1.1 MPa) when w_IBwas 5%. The synthesized hydrogels with high mechanical strength and low friction coefficient are potential candidate materials for artificial cartilage.     

会变形的水凝胶

本实验是关于可变形水凝胶的制备及其复杂形变的设计和调控的新创综合实验。首先,利用自由基聚合交联法制备含有聚丙烯酸钠(PNaAAc)的聚乙烯基吡咯烷酮-聚丙烯酰胺(PVP-PAAm)水凝胶。该凝胶具有优良的力学性能,其中PNaAAc可与Fe3+等金属离子络合,从而增加水凝胶的交联密度,降低其溶胀程度。使用离子转移印花技术和新开发的离子墨水打印技术在凝胶单面或双面不同位置引入Fe3+交联,改变水凝胶局部表面的交联密度和溶胀性能。处理后的凝胶样品在溶胀或去溶胀时可发生由一维到二维、二维到三维以及简单三维到复杂三维的复杂可控形变。