The design and synthesis of supramolecular self‐healing polymers with high healing efficiency and excellent integrated mechanical properties is challenging due to conflicting attributes of dynamic self‐healing and mechanical properties. Herein, this study introduces a design concept, that is, “dynamic hard domains,” to balance self‐healing performance, mechanical strength, elastic recovery, and at the same time obtain extreme toughness. The essential features of the dynamic hard domains include: (i) a noncrystallized and loose structure, (ii) low binding energy and high mobility, and (iii) sequential dissociation and rapid rearrangement. Based on this strategy, a simple one‐step polycondensation route is reported to synthesize a transparent polyurethane‐urea supramolecular elastomer (PPGTD‐IDA), which successfully combines decent mechanical strength, extreme toughness, outstanding notch‐sensitiveness, self‐recoverability, and room‐temperature self‐healing. Upon rupture, the PPGTD‐IDA completely restores the mechanical properties within 48 h. Furthermore, the results demonstrate repeatable healing of mechanical properties and prominent antiaging healability. Taking advantages of merits of PPGTD‐IDA, it can be utilized for fabricating impact‐resistant materials for protection of aluminum alloys as well as stretchable and self‐healing conductors, which exhibits unique characteristics such as stable conductivity during stretching (even after healing or with notch), and automatic elimination of the notch during stretching/releasing cycles.
We designed and synthesized acolorless transparent glassy polyurethane assembled using low-molecular-weight oligomers carrying al arge number of loosely packed weak hydrogen bonds (H-bonds), which has ag lass transition temperature (T g)u pt o3 6.8 8 8Ca nd behaves unprecedentedly robust stiffness with at ensile Youngsm odulus of 1.56 AE 0.03 GPa. Fast room-temperature self-healing was observed in this polymer network:t he broken glassy polyurethane (GPU) specimen can recover to at ensile strength up 7.74 AE 0.76 MPaa fter healing for as little as 10 min, whichi s prominent compared to reported room-temperature self-healing polymers.T he high density of loose-packedh ydrogen bonds can reversibly dissociate/associate belowT g of GPU (that is secondary relaxation), which enables the reconfiguration of the damaged network in the fractured interfaces,despite the extremely slow diffusion dynamics of molecular chains under room temperature.T his GPU shows potential application as an optical lens.
Polyurethane or polyurea elastomers with superb mechanical strength and toughness, good self-recoverability and healable characteristics are of key significance for practical applications. However, some mutually exclusive conflicts among these properties...
Stretchable and autonomously self-healable elastomers with wide-ranging tunable mechanical properties have attracted increasing attention in various industries. To date, it continues to be a huge challenge to synthesize selfhealing elastomers integrating extreme stretchability, relatively high mechanical modulus, and autonomous and rapid selfhealing capability. Herein, we propose a novel covalent/ supramolecular hybrid construction strategy, in which the covalent cross-links are responsible for providing high modulus and elasticity, while supramolecular cross-links realize extreme stretchability and rapid self-healing under room temperature depending on the ultrafast exchange kinetics of metal−ligand motifs and multicoordination modes. The representative polyurea hybrid elastomer, CSH-PPG-Zn-0.25, can be stretched more than 180× its original length with the highest Young's modulus (1.78 ± 0.08 MPa) among reported ultrastretchable materials. CSH-PPG-Zn-0.25 can fully restore mechanical properties of completely cut samples within 3 h. Note that the healing process can take place under a low temperature of −20 °C and unaffected by surface aging and atmospheric moisture. Merely tailoring the molar ratio of metal/ligand actualizes wide-ranging tunability of mechanical and dynamic properties, such as Young's modulus (from 1.71 ± 0.08 MPa to 5.56 ± 0.22 MPa), maximum tensile strength (from 0.32 ± 0.03 MPa to 4.42 ± 0.23 MPa), strain at break (from >18000% to 630 ± 27%), and storage modulus, ascribed to the increase of cross-linking density and formation of stiff ionic clusters. On the basis of the different material characteristics, two typical elastomers are employed, respectively, as flexible and self-healable conductor and self-healable automotive paint. Benefiting from the fantastic antiaging and low-temperature healing features of CSH-PPG-Zn-0.25, the prepared Ag-NWs/ CSH-PPG-Zn-0.25 conductor can even regain its conductive function below zero. CSH-PPG-Zn-0.50 material, meeting the strict mechanical requirements of automotive paints, is able to thoroughly eliminate the surface scratches and recover anticorrosion function in the local damaged region under the atmospheric environment.
Self-healing polymers
with microphase-separated structure are plagued
with inferior self-healing efficiency at room temperature due to a
lack of dynamic interactions in hard domains. Herein, we describe
a novel strategy of multiphase active hydrogen bonds (H-bonds), toward
realizing fast and efficient self-healing at room temperature, even
under harsh conditions. The core conception is to incorporate thiourea
moieties into microphase-separated polyurea network to form multistrength
H-bonds, which destroy the crystallization of hard domains and, at
the same time, insert the dynamic reversible H-bonds in both hard
and soft segments, accounting for the surprisingly self-healing performances.
The synthesized polymeric material, poly(dimethylsiloxane)–4,4′-methylenebis(phenyl
isocyanate)–1,1′-thiocarbonyldiimidazole, completely
recovers all of the mechanical properties within 4 h at room temperature
after rupture. Significantly, self-healing process can also take place
at low temperature (restoration with an 85% efficiency in 48 h at
−20 °C) or in the water (restoration with a 95% efficiency
in 4 h). Depending on the cleavage/reformation of multiphase H-bonds,
the material exhibits unprecedented ultrastrechability and notch-insensitiveness.
It can be stretched up to 31 500% without fracture and reach
a notch-insensitive stretching of up to 18 000%. These exceptional
characteristics inspired us to fabricate highly stretchable self-healable
underwater conductor and protective self-healing film for suppressing
shuttling of polysulfides and preventing crack propagation in S cathode,
which provide the pathway for applications in underwater electronic
devices or advanced Li–S batteries.
Background:The bacteria effector Tae4 is injected into the recipient cells to kill them and the immunity protein Tai4 is produced to inactivate Tae4. Results: Tae4 displays a papain-like fold, and Tai4 dimer is responsible for inhibiting Tae4 activity.
Conclusion:The inactivation of Tae4 is required by collaboration of both subunits of Tai4 dimer. Significance: Our results add new insights into the effector-immunity interaction module.
Background: Functional genomics has received considerable attention in the post-genomic era, as it aims to identify function(s) for different genes. One way to study gene function is to investigate the alterations in the responses of deletion mutants to different stimuli. Here we investigate the genetic profile of yeast non-essential gene deletion array (yGDA, ~4700 strains) for increased sensitivity to paromomycin, which targets the process of protein synthesis.
Background: Numerous functional genomics approaches have been developed to study the model organism yeast, Saccharomyces cerevisiae, with the aim of systematically understanding the biology of the cell. Some of these techniques are based on yeast growth differences under different conditions, such as those generated by gene mutations, chemicals or both. Manual inspection of the yeast colonies that are grown under different conditions is often used as a method to detect such growth differences.
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