Aromatic Disulfides Research Articles

Self-healing electronic skin with high fracture strength and toughness.

Human skin is essential for perception, encompassing haptic, thermal, proprioceptive, and pain-sensing functions through ion movement. Additionally, it is mechanically resilient and self-healing for protection. Inspired by these unique properties, researchers have attempted to develop stretchable, self-healing sensors based on ion dynamics. However, most self-healing sensors reported to date suffer from low fracture strength and toughness. In this work, we present an ion-based self-healing electronic skin with exceptionally high fracture strength and toughness. We enhanced self-healing polymers and ionic conductors by introducing two types of orthogonal dynamic crosslinking bonds: dynamic aromatic disulfide bonds and 2-ureido-4-pyrimidone moieties. These dynamic bonds provide autonomous self-healing and high mechanical toughness even in the presence of ionic liquids. As a result, our self-healing polymer and self-healing ionic conductor exhibit remarkable stretchability (700%, 850%), fracture strength (34 MPa, 30 MPa), and toughness (78.5MJ/m3, 87.3MJ/m3), the highest values reported among self-healing ionic conductors to date. Using our materials, we developed various fully self-healing sensors and a soft gripper capable of autonomously recovering from mechanical damage. By integrating these components, we created a comprehensive self-healing electronic skin suitable for soft robotics applications.

Multifunctional poly(ether‐urethane) elastomer based on dynamic phenol-urethane and disulfide bonds: Simultaneously showing superior toughness, self-healing, shape memory, antibacterial, and antioxidative properties

Multifunctional polymers are highly desirable for developing smart materials in medical applications. This study proposed a facile strategy to fabricate a new multifunctional poly(ether‐urethane) incorporating disulfide bonds and phenol-urethane bonds (PEU−TS). The distinctive feature of the designed PEU−TS elastomers was the presence of abundant phenolic hydroxyl groups, dynamic aromatic disulfide bonds, phenol-urethane bonds, and multiple H-bonds between urethane groups and tannic acid (TA) molecules, which endowed the materials with superior antibacterial and antioxidative activities, self‐healing capabilities, and shape memory functions. Furthermore, the phenol-carbamate crosslinked networks enhanced the tensile properties and improved the biostability of the elastomers. Biocompatibility evaluation further demonstrated that networked PEU−TS composites possessed favorable cell viability and high cytocompatibility. The multifunctional PEU−TS elastomers with robust tensile properties hold great potential for application in durable implants and chronic wound dressings. This elaborate design could inspire the development of multifunctional PU materials over wide medical applications.

In-drop capillary spooling and shape-memory behavior of microfiber made from self-healing thermoplastic polyurethane with supramolecular interactions and dynamic covalent bonds

Self-autonomic repair or self-healing is a property of materials that enables them to automatically heal their surfaces from damage, such as scratches and cracks. Intrinsic self-healing has recently garnered significant attention because it can semi-permanently reform the bonds between cracked surfaces. This paper reports the synthesis of thermoplastic polyurethane (TPU) microfibers that heal intrinsically because of multiple hydrogen bonds and disulfide metathesis. The synthesized TPUs contain ureido-pyrimidinone and aromatic disulfide moieties, which form supramolecular interactions and dynamic covalent bonds. The TPU surfaces coated on glass substrates are scratched by a blade, they heal and return to their original state after heat treatment for one hour. The mechanical properties of the TPUs are maximized when the disulfide to quadruple hydrogen bond ratio is 3:7 (TPU-S3U7). Their self-healing efficiency can be improved further by adding more disulfide bonding moieties. As a result, this TPU exhibits the shape-memory effect, and the wet-spun microfibers are completely spooled by buckling into a silicone oil droplet with a diameter of 400 µm. This soft actuating materials can be applied to smart technologies such as smart textiles, smart medical implants, and soft robotics.

Spider silk-inspired supramolecular polydimethylsiloxane network with prominent mechanical robustness for bifunctional flexible electronics

Self-healing and recyclable polymer elastomers are being developed to provide new prospects in building sustainable societies. Nevertheless, the synthesis of such materials still poses a significant difficulty because of the conflicting requirements between the self-healing ability and mechanical robustness for the dynamicity of crosslinks. Herein, a self-healing and recyclable supramolecular polydimethylsiloxane with outstanding tensile stress and ultrahigh mechanical toughness is constructed by synergistically incorporating dynamic disulfide bonds and multiple hydrogen bonds into a siloxane chain. The adipic dihydrazide (AD) bearing two hydrazide groups is appropriate introduced to provide multiple hydrogen bonding sites between polymer chains and improve the mechanical robustness of the crosslinked structure. The aromatic disulfide bonds contribute to shorter healing time due to the elevated dynamicity of the crosslinked network. The resulting elastomers exhibit high tensile strength (6.44 ± 0.24 MPa), distinguished toughness (37.00 ± 0.85 MJ m−3), superior elastic restorability, outstanding self-healing capability (∼86 %) and multiple recyclability. Furthermore, a bifunctional sensor based on this elastomer is constructed to monitor human motions and pressure changes, demonstrating the potential application in flexible stretchable electronics.

Adjusting the dynamic and mechanochromic properties of aromatic disulfide epoxy vitrimers by unsaturation of epoxy monomers

AbstractDisulfide‐contained vitrimers that possess unprecedented functions, such as reprocessing and self‐healing, are considered to be one of the most promising materials since they also exhibit mechanochromic behaviors. A few reports have given the phenomenon of mechanochromism, but the relationship between their structure and mechanochromic behavior needed to further research. Herein, three aromatic disulfide‐contained epoxy vitrimers with different degree of unsaturation are prepared by changing the epoxy monomer. The effect of network structure on the dynamic and mechanochromic properties are investigated. With increasing the degree of unsaturation from the aliphatic to aromatic epoxy vitrimers, the Tg‐value increases and the chain mobility decreases, so the aliphatic epoxy vitrimers shows the lowest activation energy, the lowest temperature of malleability Tv, and the shortest relaxation times. In addition, these epoxy vitrimers all showes reversible mechanochromic behaviors due to the generation and coupling of sulfenyl radicals, which can be accelerated by the high temperature and solvent. Meanwhile, the epoxy structure has a great influence on the mechanochromic behavior, including the absorption wavelength and fading kinetics of grinding powders. These results can be utilized to design desired vitrimer materials for various applications that requires both the intrinsically self‐report damage and the dynamic properties such as recycling.

A self-healing sustainable halloysite nanocomposite polyurethane coating with ultrastrong mechanical properties based on reversible intermolecular interactions

Endowing sustainable polyurethane (PU) materials with ultrastrong mechanical properties and highly efficient self-healing performancesimultaneously is extremely challenging and of great significance to dramatically extend the service life of metal materials. In this work, 4,4′-dithiodianiline (DTDA) and bio-based 2,5-Tetrahydrofurandimethanol (THFDM) were used as chain extenders to introduce hierarchical hydrogen bonds and aromatic disulfide bonds into the PU matrix, after which rich interfacial hydrogen bonds were obtained by incorporating environment-friendly polydopamine-modified halloysite nanotube (PDA@HNT) into the PU matrix. The developing PU nanocomposite exhibits record toughness (774.4 MJ m−3), outstanding tensile strength (68.3 MPa), and exceptional elongation at break (2882.7 %), as well as distinguished self-healing performance (85.4 % at 35 °C for 24 h; 95.9 % at 80 °C for 15 min). Thanks to the shielding effect of PDA@HNT fillers, the PU nanocomposite also possesses good corrosion resistance proved by its high impedance value at 0.01 Hz of 2.23 × 108 Ω cm2 after immersing in 3.5 wt% NaCl solution for 30 days. This work provides constructive guidance to create an ultra-robust self-healing sustainable PU nanocomposite with long-term corrosion resistance.

Highly stretchable, sensitive and healable epidermal electronics enabled by dynamic hard domains and multidimensional conductive fillers for human motion and biopotential sensing

Integration of self-healing ability and biomimetic structures into epidermal electronics is of great interest. Herein, mimicking the merits of human skin, dynamic hard domains and multidimensional conductive fillers were introduced into epidermal electronics. Firstly, aromatic disulfide bonds and H-bonds as dynamic hard domains from bis-(4-aminophenyl) disulfide and tetraethylene glycol were incorporated into polyurethane-urea (PU), and provided desired mechanical properties and self-healing capability. To enhance the strength and toughness, ZIF-67 nanoparticles with micro-pores and uncoordinated imidazole groups were introduced into PU matrix, producing excellent filler-matrix interfaces owing to the formation of high-density H-bonds and mechanical insertion. The optimized PU/ZIF-6710% composite exhibited high performance with a tensile strength of 4.15 MPa, an elongation at break of 1342.31 %, a toughness of 40.73 MJ m−3, a fracture energy of 157.75 kJ m−2, and healing efficiency of 93.25 %. Benefiting from the supramolecular PU with dynamic hard domains and multidimensional conductive fillers, the as-prepared multifunctional films exhibited excellent self-healing ability and sensing performance with a wide detection range (609 %), high sensitivity (3416.71), fast response time (65 ms), low detection limit (0.026 %), and excellent robustness (∼1000 cycles at 50 % strain). Different human motions and high-quality electrophysiological signals were successfully detected by the original and healable epidermal electrodes.

Aromatic Disulfide Cross-Linkers for Self-Healable and Recyclable Acrylic Polymer Networks

Aromatic Disulfide Cross-Linkers for Self-Healable and Recyclable Acrylic Polymer Networks

Rapid stress relaxation and degradable aromatic disulfide vitrimer for recyclable carbon fiber reinforced composite

Rapid stress relaxation and degradable aromatic disulfide vitrimer for recyclable carbon fiber reinforced composite

A multi-functional polyurethane elastomer with high damping, water resistance and flame retardancy

Polyurethane elastomer has become a current focal point in the field of damping materials due to superior comprehensive properties. However, its effective damping temperature range is limited, and existing methods often lead to a reduction in mechanical performance. Moreover, polyurethane exhibits poor water resistance and flame resistance, constraining its applications. In this study, we introduce a small amount of dangling chain and aromatic dynamic disulfide bond into polyurethane to achieve a balance between damping and mechanical performance. Notably, the fluorinated dangling chain improves water resistance of the material synchronously and effectively. Additionally, ammonium polyphosphate modified by melamine and diethyl bis(2-hydroxyethyl)aminomethylphosphonate are introduced into polyurethane to improve flame resistance. The prepared polyurethane elastomer exhibits excellent comprehensive performance, featuring an effective damping (tanδ≥0.3) temperature range of 153.2 °C (−53.2 °C ∼ 100 °C), V-0 level flame resistance and excellent water resistance. Meanwhile, the heat stability of the polyurethane elastomer has been significantly enhanced, while maintaining a certain level of mechanical performance (9.72 ± 0.25 MPa, 602.4 ± 30.1%). These improvements extend the service life of polyurethane and expand its range of potential applications.

Multifunctional aqueous polyurethanes with high strength and self-healing efficiency based on silver nanowires for flexible strain sensors.

Advanced sensor technology is widely applied in human motion monitoring and research. However, it often encounters problems such as scratches, fractures, and aging, which affect its lifespan and reliability. To address these challenges, we draw inspiration from the inherent self-healing properties of organic biological entities in nature to endow our sensors with self-healing capability. In this work, we constructed a reversible multi-hydrogen-bonded physical crosslinking network and introduced aromatic disulfide bonds into the polyurethane backbone. This design not only achieves a very high mechanical strength of the material, but also efficient self-healing properties. At 80 °C, the tensile strength of the WPU-U2D1 material reached 28.88 MPa, with a fracture elongation of 748.64%, and a self-healing efficiency as high as 99.24%. Based on this material, we successfully prepared a flexible conductive composite film (WPU@AgNW) and applied it to flexible strain sensors. The sensor demonstrated excellent sensitivity and reliability in human motion monitoring (electrical conductivity of 2.66 S cm-1), which provides a new idea for realising the breakthrough of high-performance flexible sensors. These outstanding properties makes it have great potential for application in flexible wearable devices, human-computer interaction, bionic electronic devices and other fields.

Synergistic enhancement of the robustness of multifunctional polyurethane via an ionic noncovalent cross-linking network and aromatic disulfides

The preparation of functional polyurethane materials with high strength, toughness, and excellent self-healing ability is currently challenging. In this study, a multifunctional bi-dynamic supramolecular crosslinked network PU elastomer was successfully prepared by introducing ionic bonds and aromatic disulfide bonds into a PU matrix. The resulting ionic PU elastomers exhibited impressive mechanical properties, including high tensile strength (39.9 ± 4.4 MPa) and excellent elongation at break (1930 ± 345 %). They also demonstrated efficient self-healing capability (94.4 %), recyclability and processability. The distribution of hydrophilic ion bonds within the polymer networks enabled the elastomers to possess water-induced shape memory and antibacterial activity. Additionally, the hydrophilicity of the elastomers provided a self-cleaning ability when used as a coating material. The covalent bonding of the cations with the PU matrix prevented the leaching of bactericidal substances, ensuring good biocompatibility of the ionic PU. Furthermore, a double-layered self-healing composite flexible sensor was developed using the ionic PU as the substrate and carboxylated carbon nanotubes (CNTs-COOH) as the conductive medium to detect human motion. These multifunctional ionic PU elastomers offer great potential for the design and preparation of robust materials with self-healing ability for various applications across multiple fields.

Synthesis of Symmetrical Disulfides by an NIS/PPh3-Mediated Reductive Self-Coupling of Sulfonyl Hydrazides

AbstractThe present study discloses an NIS/PPh3-mediated reductive self-coupling of arylsulfonyl hydrazides to prepare symmetric diaryl disulfides. This methodology has a broad functional-group tolerance and a high scalability. This strategy permits the introduction of sulfonyl hydrazides into the synthesis of symmetrical organic disulfides without the use of a catalyst or base, and symmetrical aromatic disulfides can be prepared in moderate to excellent isolated yields from inexpensive and readily available starting materials.

Coded Interlocked Covalent Adaptable Networks Enabled by Parallel Connections of Cation−π Interactions and Aromatic Disulfide Bonds in Epoxy

Coded Interlocked Covalent Adaptable Networks Enabled by Parallel Connections of Cation−π Interactions and Aromatic Disulfide Bonds in Epoxy

Mechanochemical Nickel-Catalyzed Carbon-Sulfur Bond Formation between Aryl Iodides and Aromatic Sulfur Surrogates.

The formation of aromatic thioethers from C-S coupling is of great importance in synthetic chemistry. Traditional solution strategies through transition-metal catalysis generally require bulk solution, heat, and longer reaction time. Herein, a mechano-promoted sulfenylation of aryl iodides with nickel catalysis is described. The active aromatic sulfide agents are in-situ generated from aromatic thiol or disulfide and subsequently adapted in the nickel catalytic cycle, with a tolerance of broad substituted groups under optimized conditions. In addition to the gram-scale synthesis that reveals the application potential of the method, the radical trapping and competitive experiments are also conducted for the mechanistic study, thus providing a plausible mechanism rationally. Furthermore, the proposed methodology is certificated as being versatile and following the green principles with ideal calculated values of green chemistry metrics, and the comparison with other approaches for C-S bond formation is also demonstrated.

Screening, Synthesis and Biochemical Characterization of SARS-CoV-2 Protease Inhibitors.

The severe acute respiratory syndrome-causing coronavirus 2 (SARS-CoV-2) papain-like protease (PLpro) and main protease (Mpro) play an important role in viral replication events and are important targets for anti-coronavirus drug discovery. In search of these protease inhibitors, we screened a library of 1300 compounds using a fluorescence thermal shift assay (FTSA) and identified 53 hits that thermally stabilized or destabilized PLpro. The hit compounds structurally belonged to two classes of small molecules: thiazole derivatives and symmetrical disulfide compounds. Compound dissociation constants (Kd) were determined using an enzymatic inhibition method. Seven aromatic disulfide compounds were identified as efficient PLpro inhibitors with Kd values in the micromolar range. Two disulfides displayed six-fold higher potency for PLpro (Kd = 0.5 µM) than for Mpro. The disulfide derivatives bound covalently to both proteases, as confirmed through mass spectrometry. The identified compounds can serve as lead compounds for further chemical optimization toward anti-COVID-19 drugs.

Thermally recyclable and reprocessable glass fiber reinforced high performance thermosetting polyurethane vitrimer composites

Glass fiber reinforced polymer composites (GFRPCs) based on thermoset polymer have been deployed in a variety of industrial sectors. However, a major drawback of thermoset polymeric composites is their significant contributions to waste and environmental pollution due to the challenges in recycling, reprocessing, and reutilization. Here, a sustainable thermosetting polyurethane vitrimer is developed by forming dynamic aromatic disulfide bonds. The obtained polyurethane vitrimer exhibits good mechanical properties and remarkable reprocessability. Under a large deformation or pulverizing, it can completely restore to its original mechanical properties of 30 MPa of strength and 407% elongation at break by 5-minute thermal reparation at 100 °C. Moreover, the unique properties of the polyurethane vitrimer enables a novel technology for processing GFRPCs, namely “blocks-building” process, in which the fully cured single-layer prepregs could be effectively integrated into multiple layers.

α-Thiosubstituted boron difluoride dibenzoylmethanates

Treatment of tetraketone, in which two dibenzoylmethane groups are connected by a disulfide bridge through central (α) carbon atoms, gave a dinuclear complex containing boronodibenzoylmethanate fragments. Like an aromatic disulfide, this compound is cleaved by the action of sulfuryl chloride and bromine to form sulfenyl chloride or sulfenyl bromide derivatives. It was shown that these compounds enter into substitution and addition reactions common for sulfenyl halides, making it possible to obtain boronodibenzoylmethanate complexes containing various functional groups linked to the chelate cycle through the central carbon atom. Based on the results of studying the UV spectra of the obtained compounds, an assumption was made about the nature of the interaction of α and β substituents with the chelate ring.

Enhancing Cell Penetration Efficiency of Cyclic Oligoarginines Using Rigid Scaffolds.

Delivering therapeutic agents into cells has always been a major challenge. In recent years, cyclization emerged as a tool for designing CPPs to increase their internalization and stability. Cyclic ring(s) can protect the peptide from enzymatic degradation, so cyclic peptides remain intact. Therefore they can be good carrier molecules. In this work, the preparation and investigation of efficient cyclic CPPs are described. Different oligoarginines were designed to conjugate with rigid aromatic scaffolds or form disulfide bonds. The reaction between the scaffolds and the peptides forms stable thioether bonds, constraining the peptide into a cyclic structure. The constructs presented very efficient internalization on cancerous cell lines. Our peptides use more than one endocytic pathway for cellular uptake. In this way, short peptides, which can compete with the penetration of well-known CPPs such as octaarginine (Arg8), may be synthesized through cyclization.

Aromatic disulfide-induced self-reinforcing polyurethane elastomer with self-healability

Developing new strategies to improve the mechanical robustness of self-healing polymer materials to meet engineering requirements remains a great challenge and research focus. Herein, a self-reinforcing strategy of self-healing polyurethane (PU) elastomer is presented to achieve simultaneous giant tensile strength (33.3 ± 1.7 MPa) and toughness (141.9 ± 3.7 MJ m−3). Two chain extenders, diethyl 2,2-bis(hydroxymethyl)malonate (BDMH) and bis(4-hydroxyphenyl) disulfide, are elaborately regulated in the molecular structure to balance the mechanical and self-healing properties. On the one hand, BDMH containing abundant ester groups provide a large number of hydrogen bond (H-bond) acceptors. On the other hand, the incorporation of aromatic disulfide forms reversible hierarchical H-bonds confined to loosely-stacked hard domains and improves the physical crosslinking density, thus realizing the self-reinforcing of PU elastomer based on the strain-induced crystallization (SIC) of polytetramethylene ether glycol (PTMEG) as the soft segment. Hierarchical H-bonds with dynamic nature acting as sacrificial bonds can dissociate and regenerate and dissipate a large amount of energy, thus contributing to mechanical robustness and self-healing properties. In addition to constructing a self-healing PU elastomer with mechanical robustness, a remarkable progress over previous work is that we perform fundamental study at the molecular level and reveal the three-stage evolution of H-bonds and aggregation structure during stretching, thus revealing the SIC behavior and mechanism, which provides a theoretical basis for the strengthening and toughening of self-healing PU elastomer.