Understanding the structural evolution process after the yielding of networks in polymer nanocomposites can provide significant insights into the design and fabrication of high-performance ...nanocomposites. In this work, using hydroxyl-terminated 1,4-polybutadiene (HTPB)/organo-clay nanocomposite gel as a model, we explored the yielding and recovery process of a polymer network. Linear rheology results revealed the formation of a nanocomposite gel with a house-of-cards structure due to the fully exfoliated 6 to 8 wt% organo-clays. Within this range, nonlinear rheologic experiments were introduced to yield the gel network, and the corresponding recovery processes were monitored. It was found that the main driving force of network reconstruction was the polymer–clay interaction, and the rotation of clay sheets played an important role in arousing stress overshoots. By proton double-quantum (1H DQ) NMR spectroscopy, residual dipolar coupling and its distribution contributed by HTPB segments anchored on clay sheets were extracted to unveil the physical network information. During the yielding process of a house-of-cards network, e.g., 8 wt% organo-clay, nearly one-fourth of physical cross-linking was broken. Based on the rheology and 1H DQ NMR results, a tentative model was proposed to illustrate the yielding and recovery of the network in HTPB/organo-clay nanocomposite gel.
In this study, we developed a superstrong and reversible adhesive, which can possess a high bonding strength in the “adhesive” state and detach with the application of heating. An ionic crystal (IC) ...gel, in which an IC was immobilized within a soft‐polymer matrix, were synthesized via in situ photo‐crosslinking of a precursor solution composed of N, N‐dimethyl acrylamide (DMAA) and a melted IC. The obtained IC gel is homogenous and transparent at melt point. When cooled to the phase transition temperature of the IC, the gel turns into the adhesive with the adhesion strength of 5.82 MPa (on glasses), due to the excellent wetting of melted gel and a thin layer of crystalline IC with high cohesive strength formed on the substrates. The synergistic effects between IC, polymer networks and substrates were investigated by solid state 1H NMR and molecular dynamics simulation. Such an adhesive layer is reversable and can be detached by heating and subsequent re‐adhesion via cooling. This study proposed the new design of removable adhesives, which can be used in dynamic and complex environments.
Inspired by reversible ice adhesion, a reversible ionic crystal (IC) based gel adhesive was prepared, which showed superstrong and reversible adhesion due to the phase transition of ICs. In addition, the reversible adhesion can be adjusted by heating and light, and be effectively monitored by resistance and capacitance.
Muscles and some tough hydrogels can maintain perfect mechanical properties after millions of loading cycles owing to the anisotropic microstructures inside them. However, applications of intrinsic ...anisotropic microstructures in biological tissues and tough hydrogels are limited by the poor mechanical performance in the perpendicular direction relative to the alignment direction. Here, a universal strategy is proposed for developing hydrogels with unprecedented isotropic crack propagation resistance only depending on the interpenetrating entanglements of polymer chains (polyacrylamide (PAAM) or poly‐(1‐acrylanmido‐2‐methylpropanesulfonic acid) (PAMPS)) in deformable polymeric microspheres (PAMPS or PAAM). The deformable interpenetrating network in microspheres can transform the hydrogel from isotropic to anisotropic instantaneously in any load direction, and effectively alleviate the stress concentration at the crack tip, dissipate energy, and eliminate notch sensitivity. The best isotropic hydrogel displays an ultimate strain of 5300%, toughness of 18.9 MJ m–3, fracture energy of 157 kJ m–2, and fatigue threshold of 4.2 kJ m–2. Furthermore, the mechanical strength of hydrogels can be simply tuned by solvent replacement. The strategy presented here can be expanded to prepare other isotropic hydrogels with super tear‐resistant and anti‐fatigue properties, based on a wide variety of deformable microspheres and matrix polymers.
A universal strategy for the preparation of hydrogels with isotropic and unprecedented crack propagation resistance is presented. The hydrogels integrate the seemingly contradictory mechanical properties such as ultra‐stretchability, fatigue resistance, tear resistance, and high toughness by the interpenetrating entanglements of polymer chains in the deformable polymeric microspheres. The prepared hydrogel displays a strain of 5300%, toughness of 18.9 MJ m–3, fracture energy of 157 kJ m–2, and fatigue threshold of 4.2 kJ m–2.
The development of aqueous metal‐ion batteries has attracted great attention due to their relatively low cost and high safety levels. However, their practical applications are hindered by the ease at ...which their aqueous electrolytes freeze. Inspired by the antifreezing properties of salts and alcohol cryoprotective agents, a “two‐in‐one” cryoprotective agent, hydroxyl‐functionalized poly(ionic liquid) (PIL‐OH)‐based hydrogel electrolyte for aqueous lithium‐ion batteries (ALIBs) is developed. The synergy of both ionic hydration and hydrogen bond interactions between the PIL‐OH and water molecules impairs the hydrogen‐bond networks of water and depresses the freezing point of water below −80 °C. Benefiting from exceptional ultralow temperature tolerance, the prepared PIL‐OH hydrogel exhibits a highly enhanced low temperature adaptability and a high ionic conductivity of 0.08 mS cm−1 at −80 °C. The PIL‐OH hydrogel‐based flexible ALIBs exhibit high flexible durability and good cycling stability with 93% capacity retention over 200 cycles at −80 °C. The PIL‐OH hydrogel report herein opens up new opportunities for practical applications of wearable and flexible aqueous batteries at ultralow temperature environments, such as the North and South Poles.
Inspired by the antifreezing properties of alcohol cryoprotective agents, a “two‐in‐one” cryoprotective agent, hydroxyl‐functionalized poly(ionic liquid) (PIL‐OH)‐based hydrogel electrolyte, with a low temperature adaptability and high ionic conductivity at −80 °C (0.08 mS cm−1) is prepared. The PIL‐OH hydrogel‐based flexible aqueous lithium‐ion batteries can be operated at an ultralow temperature of −80 °C.
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•Self-powered electronic skin based on electrode potential difference can respond to dynamic/static mechanical stimulation.•The device can be prepared by simple, efficient and ...low-cost screen printing.•The use of water-soluble and biodegradable materials enables devices to be environmentally friendly during manufacturing and disposal.
Low-power or self-powered electronic skin (e-skin) is considered an important research area, as it reduces the requirements for stable energy sources in electronic systems. However, most reported self-powered e-skins can only detect dynamic mechanical stimuli, but cannot detect ubiquitous static mechanical stimuli, resulting in a significant amount of information loss. In this paper, we report a self-powered e-skin based on electrode potential difference that can detect dynamic/static mechanical stimuli with sensitivity and response time of 399 mV/kPa and 85 ms, respectively. In this device, the mechanical stimulus is converted into a voltage signal by regulating the impedance of the electrode/electrolyte interface. In the process of preparing the device, a “green” electrode ink was prepared using a water-soluble, biodegradable polymer as the binder of the active material. Owing to the printability of the ink, a patterned electrode can be formed on a flexible substrate using low-cost screen-printing technology. Finally, we designed a co-planar shared electrode structure, which effectively reduced the complexity of the circuit layout. This new device has been successfully used for information acquisition of objects and detection of physiological signals, and we believe it has significant implications for the future development of e-skins.
Tough and self‐healable substrates can enable stretchable electronics long service life. However, for substrates, it still remains a challenge to achieve both high toughness and autonomous ...self‐healing ability at room temperature. Herein, a strategy by using the combined effects between quadruple H‐bonding and slidable cross‐links is proposed to solve the above issues in the elastomer. The elastomer exhibits high toughness (77.3 MJ m−3), fracture energy (≈127.2 kJ m−2), and good healing efficiency (91 %) at room temperature. The superior performance is ascribed to the inter and intra crosslinking structures of quadruple H‐bonding and polyrotaxanes in the dual crosslinking system. Strain‐induced crystallization of PEG in polyrotaxanes also contributes to the high fracture energy of the elastomers. Furthermore, based on the dual cross‐linked supramolecular elastomer, a highly stretchable and self‐healable electrode containing liquid metal is also fabricated, retaining resistance stability (0.16–0.26 Ω) even at the strain of 1600 %.
A tough and self‐healable elastomer is prepared through a strategy by combining quadruple H‐bonding and polyrotaxane dual crosslinks. Coarse‐grained molecular dynamics simulation and low‐field solid state 1H NMR confirmed the combined effect. Highly stretchable conductors based on the elastomers provide great potential for stretchable and tough electronic devices.
Understanding the structural evolution process after the yielding of networks in polymer nanocomposites can provide significant insights into the design and fabrication of high-performance ...nanocomposites. In this work, using hydroxyl-terminated 1,4-polybutadiene (HTPB)/organo-clay nanocomposite gel as a model, we explored the yielding and recovery process of a polymer network. Linear rheology results revealed the formation of a nanocomposite gel with a house-of-cards structure due to the fully exfoliated 6 to 8 wt% organo-clays. Within this range, nonlinear rheologic experiments were introduced to yield the gel network, and the corresponding recovery processes were monitored. It was found that the main driving force of network reconstruction was the polymer-clay interaction, and the rotation of clay sheets played an important role in arousing stress overshoots. By proton double-quantum (
H DQ) NMR spectroscopy, residual dipolar coupling and its distribution contributed by HTPB segments anchored on clay sheets were extracted to unveil the physical network information. During the yielding process of a house-of-cards network, e.g., 8 wt% organo-clay, nearly one-fourth of physical cross-linking was broken. Based on the rheology and
H DQ NMR results, a tentative model was proposed to illustrate the yielding and recovery of the network in HTPB/organo-clay nanocomposite gel.
Tough and self‐healable substrates can enable stretchable electronics long service life. However, for substrates, it still remains a challenge to achieve both high toughness and autonomous ...self‐healing ability at room temperature. Herein, a strategy by using the combined effects between quadruple H‐bonding and slidable cross‐links is proposed to solve the above issues in the elastomer. The elastomer exhibits high toughness (77.3 MJ m−3), fracture energy (≈127.2 kJ m−2), and good healing efficiency (91 %) at room temperature. The superior performance is ascribed to the inter and intra crosslinking structures of quadruple H‐bonding and polyrotaxanes in the dual crosslinking system. Strain‐induced crystallization of PEG in polyrotaxanes also contributes to the high fracture energy of the elastomers. Furthermore, based on the dual cross‐linked supramolecular elastomer, a highly stretchable and self‐healable electrode containing liquid metal is also fabricated, retaining resistance stability (0.16–0.26 Ω) even at the strain of 1600 %.
A tough and self‐healable elastomer is prepared through a strategy by combining quadruple H‐bonding and polyrotaxane dual crosslinks. Coarse‐grained molecular dynamics simulation and low‐field solid state 1H NMR confirmed the combined effect. Highly stretchable conductors based on the elastomers provide great potential for stretchable and tough electronic devices.
In this study, we developed a superstrong and reversible adhesive, which can possess a high bonding strength in the “adhesive” state and detach with the application of heating. An ionic crystal (IC) ...gel, in which an IC was immobilized within a soft‐polymer matrix, were synthesized via in situ photo‐crosslinking of a precursor solution composed of N, N‐dimethyl acrylamide (DMAA) and a melted IC. The obtained IC gel is homogenous and transparent at melt point. When cooled to the phase transition temperature of the IC, the gel turns into the adhesive with the adhesion strength of 5.82 MPa (on glasses), due to the excellent wetting of melted gel and a thin layer of crystalline IC with high cohesive strength formed on the substrates. The synergistic effects between IC, polymer networks and substrates were investigated by solid state 1H NMR and molecular dynamics simulation. Such an adhesive layer is reversable and can be detached by heating and subsequent re‐adhesion via cooling. This study proposed the new design of removable adhesives, which can be used in dynamic and complex environments.
Inspired by reversible ice adhesion, a reversible ionic crystal (IC) based gel adhesive was prepared, which showed superstrong and reversible adhesion due to the phase transition of ICs. In addition, the reversible adhesion can be adjusted by heating and light, and be effectively monitored by resistance and capacitance.
To further improve the utilization rate of starch in the fermentation of Baoning vinegar, the effects of Aspergillus niger biofortification on the quality and microbial community of vinegar Pei (a ...mixture of fermentation materials) and Baoning vinegar were evaluated. The results suggested that the total acid content, a crucial parameter for vinegar production, in vinegar Pei increased by approximately 1.70 g/100 g at the end of fermentation. The utilization rate of starch and content of organic acid increased significantly after biofortification, and the content of lactic acid was the highest in Baoning vinegar, followed by acetic acid. Similarly, the total amount of free amino acids increased after biofortification, especially the content of histidine and tyrosine. The esters and acid compounds were the most abundant in the vinegar Pei, while the contents of acid and carbonyl compounds were the highest in liquid vinegar. As revealed by high-throughput sequencing, the microbial community in vinegar Pei changed little after biofortification. Lactic acid bacteria and yeast are the most abundant microbes throughout the fermentation process. The present study provides insights into the improvement of the solid-state brewing process of vinegar.
•A. niger increased the usage of starch and total acid content in vinegar Pei.•A. niger increased the amino acid content, but maintained the flavor characteristics.•The microbial community changed little in vinegar Pei after biofortification.
