Reversibly Interlocked Macromolecule Networks with Enhanced Mechanical Properties and Wide pH Range of Underwater Self-Healability

Highly Ionic Conductive, Self-Healing, Li10GeP2S12-Filled Composite Solid Electrolytes Based on Reversibly Interlocked Macromolecule Networks for Lithium Metal Batteries with Improved Cycling Stability

Ceramic-polymer composite solid electrolytes (CSEs) have attracted great attention by combining the advantages of polymer electrolytes and inorganic ceramic electrolytes. Herein, Li10GeP2S12 (LGPS) particles are incorporated into poly(ethylene oxide) (PEO)-based reversibly interlocked polymer networks (RILNs) derived from the topological rearrangement of two PEO networks cross-linked by reversible imine bonds and disulfide linkages. A series of highly ionic conductive, self-healing CSEs are obtained accordingly. The interlocking architecture successfully inhibits PEO crystallization, increasing the amorphous phase for Li ion transportation, and stabilizes the conductive pathways of LGPS particles by its unique confinement effect. Meanwhile, the LGPS particles cooperate with the RILN matrix, forming a filler-polymer interfacial phase for additional Li ion transportation and strengthening and toughening the resultant CSEs via the strong intermolecular Li+-O2- interactions. Furthermore, the dynamic characteristics of the included reversible bonds ensure a multiple intrinsic self-healing capability. Consequently, the CSEs containing 15 wt % LGPS deliver a high ionic conductivity (1.06 × 10-3 S cm-1) and high Li ion transference number (∼0.6) at 25 °C, a wide electrochemical stability window (>4.9 V), good mechanical properties (0.63 MPa, 377%), and a stable CSE/Li anode interface. The integrated Li/CSE/LiFePO4 battery exhibits a specific discharge capacity of 110.8 mAh g-1 at 1 C (25 °C) and a capacity retention of 76.9% after 200 cycles. Thanks to the healability, the damaged CSEs can regain the structural integrity, ion conductive capability, and cycling performance of the assembled cells. The present work provides an effective strategy to fabricate CSEs for lithium metal batteries that are workable at ambient temperature.

Highly flexible yet strain-insensitive conjugated polymer

Imparting excellent electrical properties, mechanical robustness, suppleness, conduction stability during deformation, and self-healing to intrinsic conducting polymers is a challenging endeavor. The reversibly interlocked macromolecular networks (RILNs) approach is utilized to tackle this problem. Specifically, poly(3,4-ethylenedioxythiophene) (PEDOT) is mixed with flexible polysulfonic acid networks crosslinked by reversible Diels-Alder bonds, while rigid polyaniline networks crosslinked by reversible Schiff base bonds act as molecular staples. Owing to the joint actions of the doping effect of polyaniline on PEDOT, the specific interlocking architecture and synergy between the component materials, the electrical conductivity (59.3-980.5 S cm-1), tensile strength (8.4-81.6 MPa) and elongation at break (44.5-411.0%) of the resultant PEDOT/RILNs films is significantly tunable according to different usage scenarios by adjusting the PEDOT content from 1.48 to 22.24 wt%. More importantly, the electrical resistance of PEDOT/RILNs remains constant during not only a single large extension and deflection but also repeated stretching (up to 1500 cycles) and bending (up to 106 cycles). The built-in reversible covalent bonds enable the PEDOT/RILNs to autonomously restore damaged mechanical and electrical performance. These record-breaking results and the demonstration of self-powered sensor made of PEDOT/RILNs suggest that the proposed approach successfully satisfies various conflicting requirements of flexible electronics regarding the properties of conducting polymers.

Recent advances in self-healing polyurethane based on dynamic covalent bonds combined with other self-healing methods

To meet more application requirements, improving mechanical properties and self-healing efficiency has become the focus of current research on self-healing PU. The competitive relationship between self-healing ability and mechanical properties cannot be avoided by a single self-healing method. To address this problem, a growing number of studies have combined dynamic covalent bonding with other self-healing methods to construct the PU structure. This review summarizes recent studies on PU materials that combine typical dynamic covalent bonds with other self-healing methods. It mainly includes four parts: hydrogen bonding, metal coordination bonding, nanofillers combined with dynamic covalent bonding and multiple dynamic covalent bond bonding. The advantages and disadvantages of different self-healing methods and their significant role in improving self-healing ability and mechanical properties in PU networks are analyzed. At the same time, the possible challenges and research directions of self-healing PU materials in the future are discussed.

Dynamic Covalent Structure for the Design of Recyclable Polyurethane Based on the Diketone Chemistry

Herein, the rational design of an enaminone compound is reported which can be easily and conveniently designed and obtained via the reaction of amine and diketone. The dynamic enaminoneamide structure is formed via the reaction between isocyanate and enaminone in fabricating a novel dynamic crosslinked polyurethane. The new kind of polyurethane can be efficiently recycled via the shifting between crosslinked structure and oligomer for the reversible dissociation of the enaminoneamide structure. Besides remolding itself via the thermal treatment, oligomers liberated from recycled-polyurethane can directly take part in constructing a new polyurethane without further purification. Therefore, the recyclability of this polyurethane shows high-value characteristics. The ease with which polyurethane can be produced, used, recycled, and reused without losing value offers a new green solution in designing sustainable polymer materials with a high economic value and a minimal environmental burden.

Water-Enhanced and Remote Self-Healing Elastomers in Various Harsh Environments

The development of underwater remote stimulus-responsive self-healing polymer materials for applications in inaccessible and urgent situations is very challenging because water can readily disturb traditional noncovalent bonds and absorb heat, UV light, IR light, and electromagnetic wave energy at the wave band of micrometers and millimeters. Herein, visible-light-responsive diselenide bonds are employed as the healing moieties to produce a water-enhanced and remote self-healing elastomer triggered by a blue laser, which possesses excellent underwater transmission capability. During healing, the strain at break reaches ∼200% in 5 min and its toughness almost fully recovers within 1 h, which is estimated to be the fastest reported to date for healing silicone elastomers with a healing efficiency above 90%. The remote underwater pipeline sealing is instantly accomplished with the diselenide-containing elastomers by a blue laser 3 m away, thereby providing a direction for future emergent healing applications.

Recyclable silicone elastic light-triggered actuator with a reconfigurable Janus structure and self-healable performance

A recyclable silicone elastic light-triggered actuator with reconfigurable Janus structure and self-healable performance is reported, which was fabricated via heterogeneous crosslinking induced by a gradient intensity of UV light due to CNTs accretion.

Dynamic Covalent Polyurethane Network Materials: Synthesis and Self-Healability

Polyurethane (PU) has not only been widely used in the daily lives, but also extensively explored as an important class of the essential polymers for various applications. In recent years, significant efforts have been made on the development of self-healable PU materials that possess high performance, extended lifetime, great reliability, and recyclability. A promising approach is the incorporation of covalent dynamic bonds into the design of PU covalently crosslinked polymers and thermoplastic elastomers that can dissociate and reform indefinitely in response to external stimuli or autonomously. This review summarizes various strategies to synthesize self-healable, reprocessable, and recyclable PU materials integrated with dynamic (reversible) Diels-Alder cycloadduct, disulfide, diselenide, imine, boronic ester, and hindered urea bond. Furthermore, various approaches utilizing the combination of dynamic covalent chemistries with nanofiller surface chemistries are described for the fabrication of dynamic heterogeneous PU composites.

Catechol-metal coordination-mediated nanocomposite hydrogels for on-demand drug delivery and efficacious combination therapy

Hydrogels have drawn considerable attention in the field of drug delivery, yet their poor mechanical strength and uncontrollable drug release behavior have hindered further applications in clinical practice. Taking utility of metal-ligand coordination for structurally reinforcing the hydrogel network, we report design and synthesis of magnetic nanocomposite hydrogels (HA-DOPA·MNPs) that are crosslinked by DOPA-Fe(III) coordination existing between dopamine-conjugated hyaluronan (HA-DOPA) and iron oxide magnetic nanoparticles (MNPs). The MNPs in the nanocomposite hydrogel not only serve as structural crosslinkers, but also facilitate magnetic hyperthermia and on-demand release of doxorubicin (DOX) in HA-DOPA·MNPs/DOX hydrogels, for release rate of DOX accelerates when external alternating magnetic field (AMF) is ON, and it restores to a slow pace when AMF is OFF. Importantly, HA-DOPA·MNPs/DOX hydrogel shows a longer retention time than HA-DOPA/DOX gel or DOX solution in vivo. Further experiments confirm the efficacious anticancer potency of HA-DOPA·MNPs/DOX in vitro and in vivo, that is mediated by a combination therapy consisting of chemotherapy (DOX) and hyperthermia (MNPs). In contrast, single-modality treatment (DOX or hyperthermia only) fails to show an equivalent efficacy at the same dose. STATEMENT OF SIGNIFICANCE: This study reports the design of a class of magnetic nanocomposite hydrogel (HA-DOPA·MNPs) that was structurally reinforced by DOPA-Fe (III) coordination between HA-DOPA and iron oxide MNPs. On one hand, MNPs served as crosslinking centers for structurally reinforcing the nanocomposite hydrogel; on the other hand, MNPs facilitated temperature rise under an external MNPs, which prompted on-demand drug release as well as a combination therapy. Comparing to single modality treatment (chemotherapy or hyperthermia alone), the HA-DOPA·MNPs/DOX formulation with AMF demonstrated better efficacy against proliferation of tumor cells (A375) both in vitro and in vivo. We believe that design of HA-DOPA·MNPs/DOX hydrogel in this report provides a general approach to fabricate structurally-reinforced nanocomposite hydrogels for on-demand drug delivery and efficacious combination therapy.