Dynamic Disulfide Bonds Research Articles

Synergistic Toughening and Self‐Healing Strategy for Highly Efficient and Stable Flexible Perovskite Solar Cells

AbstractHalide perovskites are qualified to meet the flexibility demands of optoelectronic field because of their merits of flexibility, lightness, and low cost. However, the intrinsic defects and deformation‐induced ductile fracture in both perovskite and buried interface significantly restrict the photoelectric performance and longevity of flexible perovskite solar cells (PVSCs). Here, a dual‐dynamic cross‐linking network is schemed to boost the photovoltaic efficiency and mechanical stability of flexible PVSCs by incorporating natural polymerizable small molecule α‐lipoic acid (LA). The LA therein can be autonomously ring‐opening polymerized through dynamic disulfide bonds and hydrogen bonds, concurrently forming coordination bonds to interact with perovskite component. Importantly, the polymerization product can serve as efficacious passivating and toughening agents to simultaneously optimize interfacial contact, enhance perovskite crystallinity and sustain robust mechanical bendability. Subsequently, the rigid (or flexible) p‐i‐n device realizes a champion efficiency of 22.43% (or 19.03%) with prominent operational stability. Moreover, the dual‐dynamic cross‐linking network endows PVSCs with bendability and self‐healing capacity, allowing the optimized devices to retain >80% efficiency after 3000 bending cycles, and subsequently restore to ≈95% of its initial efficiency under mild heat‐treatment. This toughening and self‐healing strategy provides a facile and efficient path to prolong operational lifetime of flexible device.

Mussel‐Inspired, Underwater Self‐Healing Ionoelastomers Based on α‐Lipoic Acid for Iontronics

Weak adhesion and lack of underwater self-healability hinder advancing soft iontronics particularly in wet environments like sweaty skin and biological fluids. Mussel-inspired, liquid-free ionoelastomers are reported based on seminal thermal ring-opening polymerization of a biomass molecule of α-lipoic acid (LA), followed by sequentially incorporating dopamine methacrylamide as a chain extender, N,N'-bis(acryloyl) cystamine, and lithium bis(trifluoromethanesulphonyl) imide (LiTFSI). The ionoelastomers exhibit universal adhesion to 12 substrates in both dry and wet states, superfast self-healing underwater, sensing capability for monitoring human motion, and flame retardancy. The underwater self-repairabilitiy prolongs over three months without deterioration, and sustains even when mechanical properties greatly increase. The unprecedented underwater self-mendability benefits synergistically from the maximized availability of dynamic disulfide bonds and diverse reversible noncovalent interactions endowed by carboxylic groups, catechols, and LiTFSI, along with the prevented depolymerization by LiTFSI and tunability in mechanical strength. The ionic conductivity reaches 1.4 × 10-6 -2.7 × 10-5 S m-1 because of partial dissociation of LiTFSI. The design rationale offers a new route for creating a wide range of LA- and sulfur-derived supramolecular (bio)polymers with superior adhesion, healability, and other functionalities, and thus has technological implications for coatings, adhesives, binders and sealants, biomedical engineering and drug delivery, wearable and flexible electronics, and human-machine interfaces.

Polysulfide polyurethane-urea(PSPU)-based self-healing dielectric composites with poly-dopamine and KH550 chemically modified carbon nanotubes

In this work, polysulfide polyurethane-urea (PSPU) elastomers with dynamic disulfide bonds introduced into both the soft and hard segments were synthesized. Carboxylated carbon nanotubes (CNT) modified with poly-dopamine and KH550 (KPCNT) were used as fillers, and an approach of solution casting was adopted to fabricate the composite films (named KPCNT/PSPU). In addition, the self-healing efficiency of KPCNT/PSPU composites is improved to 98%. The percolation threshold (fc) of KPCNT/PSPU (5.11 vol%) is about twice that of unmodified CNT/PSPU composite film (2.69 vol%). The dielectric constant of 4.74 vol% KPCNT/PSPU at 100 Hz is 141, about 23 times that of PSPU, as well as maintaining a low dielectric loss of 0.17. Furthermore, the CNT/PSPU composite with 2.45 vol% CNT has a dielectric constant of 82 at 100 Hz, while reaching a high dielectric loss of 0.72. It can be concluded that the excellent dielectric properties come from the micro-capacitor effect, interfacial polarization, the exchange of hydrogen-bonding networks as well as disulfide bonds within the PSPU.

Self-healable, stretchable triboelectric nanogenerators based on flexible polyimide for energy harvesting and self-powered sensors

Self-healing triboelectric nanogenerators (TENGs) are new, stable and durable energy harvesters. Polyimide (PI) is a promising negatively charged material that has been widely developed as a negative friction material for TENGs, but self-healing PI-based TENGs are currently vacant. Here, we reported a self-healing TENG device fabricated by self-healing PI for energy harvesting and motion sensing. The designed and fabricated PI-based TENGs exhibited excellent intrinsic self-healing and shape tailorability properties. The self-healing properties are derived from the dynamic disulfide bond exchange and flexible PDMS fragments in the PI backbone, which can recover its damage and output performance at 100 °C for 3 h. The output performance of the fabricated 6FDA-4PDA-PDMS-PI-based TENG was double that of the normal PI-based TENG due to CF3 electron-absorbing groups and siloxane fragments in the PI backbone. Finally, the applications of self-healing PI-based TENGs to harvest energy to drive commercial electronic devices and joint motion sensing were demonstrated. This work provides theoretical guidance for the fabrication of self-healing TENGs with reliable output performance and practical applications, contributing to the future of sustainable energy and wearable electronics.

Recyclable Solid–Solid Phase Change Materials with Excellent Reprocessing Properties Based on Dynamic Disulfide Bonds

Phase change materials (PCMs) with energy-saving and sustainable energy potential are widely available for energy storage technologies. At present, chemical cross-linking is often constructed to form solid–solid phase change materials (SSPCMs) to avoid leakage during the phase change process, but its permanent cross-linked network cannot be reprocessed, resulting in nonrecyclable materials with very high environmental impact. Herein, we prepare a series of poly(ethylene glycol) (PEG)-containing reprocessed solid–solid phase change materials (RSSPCMs) based on dynamic disulfide bonds, which were in the solid state even at high temperatures. These RSSPCMs had high latent heat with a maximum value of 100.2 J/g, which exhibited remarkable thermal storage capacity in addition to excellent solar-thermal conversion capacity. Interestingly, the introduction of dynamic disulfide bonds in the molecular structure provided RSSPCMs with excellent self-healing properties and recyclability. Broken RSSPCM samples could heal under thermal-induced and infrared radiation-induced reprocessing. Importantly, the chemical structure, crystallization behavior, and phase transition ability of RSSPCMs could also remain unchanged after multiple recycling. Designing RSSPCMs based on dynamic disulfide bonds is important for achieving the efficient utilization of solar energy and environmental protection.

A Self‐Healing and Nonflammable Cross‐Linked Network Polymer Electrolyte with the Combination of Hydrogen Bonds and Dynamic Disulfide Bonds for Lithium Metal Batteries

The self‐healing solid polymer electrolytes (SHSPEs) can spontaneously eliminate mechanical damages or micro‐cracks generated during the assembly or operation of lithium‐ion batteries (LIBs), significantly improving cycling performance and extending service life of LIBs. Here, we report a novel cross‐linked network SHSPE (PDDP) containing hydrogen bonds and dynamic disulfide bonds with excellent self‐healing properties and non‐flammability. The combination of hydrogen bonding between urea groups and the metathesis reaction of dynamic disulfide bonds endows PDDP with rapid self‐healing capacity at 28 °C without external stimulation. Furthermore, the addition of 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI) improves the ionic conductivity (1.13 × 10−4 S cm−1 at 28 °C) and non‐flammability of PDDP. The assembled Li/PDDP/LiFePO4 cell exhibits excellent cycling performance with a discharge capacity of 137 mA h g−1 after 300 cycles at 0.2 C. More importantly, the self‐healed PDDP can recover almost the same ionic conductivity and cycling performance as the original PDDP.

Biomimetic supramolecular polyurethane with sliding polyrotaxane and disulfide bonds for strain sensors with wide sensing range and self-healing capability.

To prolong the service life of flexible electronic materials, polymeric matrixes with excellent self-healing capability and integrated mechanical properties are highly desirable, but the balance between the self-healing capability and mechanical properties is a grand challenge. Here, polyrotaxanes as sliding crosslinkers and dynamic disulfide bonds are incorporated into the main chains of polyurethane (PU) via one-pot synthesis, which endows the PU with polydisperse hard/soft segments, high density of self-healing points and energy dissipation. Based on this judicious molecular design, the PU elastomers exhibit exceptional mechanical properties, such as high stretchability (1167% with a tensile strength of 3.49MPa), high fracture energy (20,775Jm-2) and high puncture energy (200.70mJ). Moreover, due to the presence of dynamic reversible hydrogen and disulfide bonds, the elastomer could achieve stress and strain repair efficiencies of 93.98% and 99.21% at 100 ℃ within 1h, respectively. The above-mentioned superiorities enable the bioinspired strain sensors to possess a large sensing range (∼596%), high sensitivity (∼79.98), short response time (∼128ms), along with excellent reliability and self-healing ability. Besides, the strain sensor exhibits remarkable recyclability and prominent reprocessability, which nicely solves the pollution by discarded electronics.

Hemiaminal dynamic covalent networks with rapid stress relaxation, reprocessability and degradability endowed by the synergy of disulfide and hemiaminal bonds.

This work proposes a strategy to address the challenge of achieving rapid reprocessability of vitrimers at mild temperatures by introducing dynamic disulfide and hemiaminal bonds into hemiaminal dynamic covalent networks (HDCNs). The resulting HDCNs, termed HDCNs-DTDA, were prepared through a facile polycondensation between formaldehyde and 4,4'-dithiodianiline. The dual dynamic bond system in the HDCNs-DTDA enables rapid stress relaxation under mild temperature (65 °C for 54 s), which is significantly faster than that observed in HDCNs containing a single dynamic bond (HDCNs-DDM). The HDCNs-DTDA also exhibit a glass transition temperature of 96 °C, excellent solvent resistance and high recovery rates (97%) of tensile strength after reprocessing. In addition, HDCNs-DTDA can be easily degraded in HCl and thiol solutions at room temperature to enable chemical recyclability. Finally, HDCNs-DTDA demonstrates fast shape memory behaviors using thermal stimulation.

Dynamic disulfide bonds facilitated fabrication of a multifunctional liquid-free elastomer for recyclable soft electronics

A liquid-free ionic conductive elastomer constructed from biomass small molecules shows high transparency, self-healing ability, recyclability/degradability, and conductivity as well as mechanical strength.

Self-healable and reprocessable networks of poly(propylene oxide) with POSS crosslinked with disulfide bonds

The organic-inorganic networks involving poly(propylene oxide) (PPO) and POSS were synthesized via the in situ crosslinking with disulfide bonds. First, a tri-armed PPO star with amino termini was reacted with 4-(phenoxymethyl)-1,3-dithiolane-2-thione, a cyclic five-membered thiocarbonate to obtain the tri-armed PPO star with mercapto thiourethane termini. In the meantime, 4-aminobutylhepta(3,3,3-trifloroproply) POSS was also reacted with 4-(phenoxymethyl)-1,3-dithiolane-2-thione to obtain a mercapto thiourethane -functionalized POSS macromer. Thereafter, both PPO star and POSS macromer which contained mercapto thiourethane moieties were co-crosslinked via the radical coupling reaction, in which the thiol groups were coupled into disulfide bonds. The POSS-containing PPO networks were microphase-separated. It was found that the POSS cages grafted onto PPO networks were self-organized into the spherical nanodomains. Compared to the control network, the nanocomposites displayed the improved thermomechanical properties and surface hydrophobicity. More importantly, the organic-inorganic networks were self-healable and can be repeatedly processed without sacrificing the mechanical strengths. The exchange reaction of dynamic disulfide bonds is attributable to the self-healing or/and reprocessing properties. In addition, the break and reform of the POSS microdomains are also contributable to the reprocessing behavior at elevated temperature.

Skin-friendly and antibacterial monodomain liquid crystal elastomer actuator

Monodomain liquid crystal elastomers (mLCEs) are flexible and biocompatible smart materials that show unique behaviors of soft elasticity, anisotropy, and reversible shape changes above the nematic-isotropic transition temperature. Therefore, it has great potential for application in wearable devices and biologically. However, most of the reported mLCEs have nematic-isotropic transition temperature (TNI) higher than 60 °C; and above this TNI, the tensile strength of the mLCEs decreases by orders of magnitude. These issues have received little attention, limiting their application in humans. Herein, the TNI of mLCEs was reduced from 78.4 °C to 23.5 °C by substituting part of the rigid LC mesogens with a flexible backbone. The physical entanglement of hydrogen bonds between molecular chains alleviated the molecular chain slip caused by the long flexible backbone. The tensile strength remained constant during the phase transformation. Furthermore, dynamic disulfide bonds were used to modify the LC polymer network, imparting it with excellent antimicrobial, programmable, and self-healing properties. To realize its application in the closure of skin wounds, a porous PHG–mLCE/hydrogel patch that was breathable and waterproof was designed to increase skin adhesion (262 N/m).

UV-curable castor-oil-based multi-crosslinking polymer networks containing dynamic disulfide bonds: High toughness, self-healing, and shape memory properties

Novel functional dynamic covalent-bonded polymer networks (DCPN) containing dynamic disulfide bonds were prepared from castor oil via a simple process. Firstly, UV-curable castor-oil-based polyurethane acrylate (COPUA) containing disulfide bonds and unsaturated double bonds was synthesized, then added with glycidyl methacrylate (GMA) to reduce viscosity (named COPUA-GMA) and mixed with different proportions of glycidyl esters containing unsaturated double bonds to form a series of UV-cured polymers named COPUA-GMA-EP. FTIR and NMR demonstrated the target pre-polymers and DCPNs were successfully synthesized. The DCPNs possessed controllable mechanical properties. Tensile tests showed the polymers had a range of tunable stiffness and flexibility. The COPUA-GMA-EP-2 copolymerized system containing 50 wt% COPUA-GMA had relatively excellent tensile strength of 11.8 MPa and elongation at break of 72.3%. Thermal analysis showed that DCPNs had excellent thermal stability, and COPUA-GMA-EP-2 had higher crosslinking density. Importantly, COPUA-GMA-EP-2 displayed excellent shape memory properties with Rf of 98.9% and Rr of 79.0%. Meanwhile, this DCPN exhibited certain self-healing properties. The DCPNs will be widely applied with good prospects owing to their excellent UV-curable, eco-friendly and shape memory properties.

Limonene-thioctic acid-ionic liquid polymer: A self-healing and antibacterial material for movement detection sensor

The healable smart electronic sensor can prolong its service life. Polymers with dynamic disulfide bonds are widely used in healable sensors because of their self-healing properties at room temperature, but the presence of terminal diradicals leads to their instability. Herein, attracted by the favorable reactivity of limonene (LIM) for nucleophilic proton addition, it is chosen to quench thiyl radical to prepare a self-healing polymeric material (poly TA-(EMIM)(ESO 4 )-LIM) for the sensor by thioctic acid (TA) and 1-ethyl-3-methylimidazolium ethyl sulfate [(EMIM)(ESO 4 )]. The polymeric material not only displayed long-term stability and moderate strain (640%) but also was equipped with a high adhesive strength towards various substrates. The existence of dynamic disulfide bonds and the hydrogen bonds conferred favorable self-healing capacity of the poly TA-(EMIM)(ESO 4 )-LIM. The fascinating conductivity sensitivity with gauge factors of 2.34 and 5.12 could be achieved under small deformation (0%−100%) and large deformation (100%−200%), respectively. Meanwhile, the polymeric material could detect the human movement of finger bending, elbow bending, and wrist bending, where a stable conductivity sensitivity could maintain after several cycles. Moreover, based on the natural and outstanding antibacterial activity of LIM, the antimicrobial capacity of the polymeric material is further enhanced (kill efficiency > 90%). These fascinating features make the poly TA-(EMIM)(ESO 4 )-LIM displayed great potential as an epidermal electronic for detecting human movement. • A polymeric material was obtained by limonene, thioctic acid, and ionic liquid. • The polymeric material could realize rapid network reconfiguration. • The polymeric material displayed over 90% kill efficiency towards bacteria. • The polymeric material displayed high sensitivity in detecting human movements.

Preparation of self-healing epoxy resin coatings based on dynamic disulfide bonds

Defects and mechanical damage that lead to peeling, corrosion and other potential hazards during practical applications are inevitable in epoxy coatings due to the high cross-link density of the epoxy network. Herein, the authors synthesized a self-healing polythiourethane (SPTU) material containing dynamic disulfide bonds for the design and preparation of an SPTU–epoxy coating. Fourier transform infrared spectroscopy, proton (1H) nuclear magnetic resonance spectroscopy and scanning electron microscopy showed that 2-hydroxyethyl disulfide was successfully introduced into the polythiourethane system. Due to the fracture and reattachment of double sulfur bonds, the 3% SPTU–epoxy coating exhibited good self-healing properties in scratch treatment, the scratch being repaired completely after 2 h at 85°C. Meanwhile, 75.7% of the tensile performance of the completely fractured 3% SPTU–epoxy sample was retained after self-healing. The Tafel polarization curve and electrochemical impedance spectroscopy results showed that the 3% SPTU–epoxy coating had excellent corrosion resistance and still provided considerable corrosion resistance after 19 days of immersion corrosion tests. The self-healing coating exhibited good self-healing ability under heating conditions, which is attributed to the bond breaking and reconnection of dynamic bonds provided by the self-healing component. The self-healing properties and corrosion resistance of the prepared coating effectively improve the service life of the epoxy coating and provide some guidance for corrosion protection of epoxy coatings.

Multifunctional Waterborne Polyurethane Microreactor-Based Approach to Fluorocarbon Composite Latex Coatings with Double Self-Healing and Excellent Synergistic Performances.

In this article, chlorotrifluoroethylene (CTFE)-based fluorocarbon composite latexes and their coatings are successfully fabricated by an environmentally friendly preparation method based on a new multifunctional waterborne polyurethane (MFWPU) dispersion. It is worth noting that the MFWPU acts as the sole system stabilizer as well as microreactor and simultaneously endows the composite coating with excellent double self-healing performance and adhesion. Moreover, the introduction of a dynamic disulfide bond in the polyurethane dispersion entrusts the coating with excellent scratch self-healing performance. Simultaneously, carbon-carbon double bonds in the polyurethane dispersion increase the compatibility between the core polymer and shell polymer. The fluorine-containing chain segments can be distributed in the coating evenly during the self-assembly film-forming process of composite particles so that the original element composition of the worn coating surface can restore the original element composition after heating, and the coating presents a regeneration ability, which further and verifies the usefulness of the double self-healing model of the coating. Afterward, efficient recovery and durability, which are two contradictory properties of scratch self-healing polymers, are optimized to obtain a composite coating with excellent comprehensive performance. The research results regarding the composite system may provide a valuable reference for the structural design and application of waterborne fluorocarbon functional coatings in the future.

Design of epoxidized natural rubber/poly(lipoic acid) elastomer with fast and efficient self-healing under a mild temperature

Most of the dynamic covalent bonds (DCBs) for self-healing rubber must be activated at relatively high temperatures due to the requirement of high energy during the exchange of dynamic bonds, which may lead to unexpected degradation or excessive crosslinking of rubber. Herein, we designed and fabricated a highly stretchable, self-healable and reprocessable rubber by introducing dynamic disulfide bonds into the crosslink network of epoxidized natural rubber (ENR). Lipoic acid (LA) was firstly uniformly dispersed into ENR via a latex film formation technique, and then underwent a dynamic covalent ring-opening self-polymerization during hot pressing process, during which the carboxyl group of poly(LA) attacked the epoxy group of ENR to form β-hydroxyl ester bond crosslinks. As a result, a revisable covalently crosslinked network without rigid steric hindrance groups was constructed, which exhibited a super self-healing efficiency of 99 % after self-healing at 80 °C for only 3 h. The elongation at break of the elastomer could reach 1115 % and the recovery rate of reprocessing was as high as 91 %.

Dynamic Disulfide Bonds Contained Covalent Organic Framework Modified Separator as Efficient Inhibit Polysulfide Shuttling in Li–S Batteries

First, a new covalent organic framework (HUT9) with disulfide bonds have been synthesized, which can be grown in situ on carbon nanotubes (CNT) as separator modification material for Li–S batteries. Experiments and DFT showed that disulfide bond could effectively capture soluble polysulfides (LiPSs) during discharge process, while promoting the conversion of LiPSs to Li2S/Li2S2 and improve the utilization rate of sulfur. The polar groups of the covalent organic framework provide chemisorption, and an interwoven network of HUT9@CNT (physical constraints) cooperates to inhibit the transport of LiPSs. The modified battery has a capacity retention rate of 83% (decay rate of 0.032% per cycle) after 500 cycles at 1 C. Specifically, the battery with 2-HUT9@CNT modified separators (sulfur loading: 4 mg cm–2, sulfur content: 80%, electrolyte/sulfur ratio: 10 mL g–1) can reach 3.4 mAh cm–2 area capacity after 50 cycles. This work enriched the COF material system and provided guidance for the application of organic materials in an energy storage system.

Transparent and Self-Healing Elastomers for Reconfigurable 3D Materials.

Transparent soft materials are widely used in applications ranging from packaging to flexible displays, wearable devices, and optical lenses. Nevertheless, soft materials are susceptible to mechanical damage, leading to functional failure and premature disposal. Herein, a transparent self-healing elastomer that is able to repair the polymer network via exchange reactions of dynamic disulfide bonds is introduced. Due to its self-healing ability, the mechanical properties of the elastomer can be recovered as well as its transparency after multiple cycles of abrasion and healing. The self-healing polymer is fabricated into 3D structures by folding or modular origami assembly of planar self-healing polymer sheets. The 3D polymer objects are employed as storage containers of solid and liquid substances, reactors for photopolymerization, and cuvettes for optical measurements (exhibiting superior properties to those of commercial cuvettes). These dynamic polymers show outstanding mechanical, optical, and recycling properties that could potentially be further adapted in adaptive smart packaging, reconfigurable materials, optical devices, and recycling of elastomers.

Room-temperature self-healing polysiloxane elastomer with reversible cross-linked network

The linear self-healing matrix had certain defects in the aspects of physical and mechanical properties, heat resistance and solvent resistance, which limited its application in engineering. However, if the conventional cross-linked structure was integrated into material matrix, the self-healing properties of the material would be sacrificed seriously. To address the drawbacks of linear and cross-linked self-healing polymers, reversible cross-linked structural units were designed to balance the two aspects. The silicone elastomers were endowed with outstanding mechanical properties and self-healing ability at room temperature by introducing a tri-functional cross-linking agent “Trimer of hexaethylene-diisocyanate (Tri-HDI)” to PDMS linear structure, and distributing dynamic disulfide bonds around of the cross-linking points to build the reversible cross-linking structural units. The influence of cross-linker content on the mechanical properties, self-healing properties and heat resistance of the elastomer was systematically investigated in this paper. Then, the soft and hard segment structures at different temperatures of the self-healing materials was characterized by low-field NMR as an innovative structural characterization. This room temperature self-healing elastomer with reversible cross-linked structure had great potential for industrial applications.

Shape reconfiguration and functional self-healing of thermadapt shape memory epoxy vitrimers by exchange reaction of disulfide bonds

Epoxy-based shape memory materials still face many challenges from preparation to application. Designing dynamic covalent bonds into the cross-linked network of epoxy can bring many new properties to them, which is expected to solve some of the problems faced. In this paper, epoxy vitrimers with different contents of exchangeable disulfide bonds were synthesized by the polymerization of hydrogenated epoxy resins with diacids containing dynamic disulfide bonds. The effect of disulfide bond content on the properties of epoxy vitrimers was systematically studied. By activating the exchange reaction of disulfide bonds, the permanent shape of epoxy vitrimers can be reconfigured, even from two to three dimensions. The time required for reconfiguring is affected by the content of disulfide bonds, the more disulfide bonds, the shorter the time required. The epoxy vitrimers with more content of disulfide bonds were found to have lower recovery ratio loss after the same shape memory cycle by thermal bending experiments. More importantly, the epoxy vitrimers with more content of disulfide bonds also exhibited better functional self-healing properties. The decreased recovery ratio can be healed by periodic heat treatment, thus ensuring that the epoxy vitrimers perform more shape memory cycles and maintain a high shape recovery ratio. These experimental results will serve as a basis for expanding the range of applications and prolonging the service life of epoxy-based shape memory materials.