Programmable and Self-Healable Liquid Crystal Elastomer Actuators Based on Halogen Bonding

Shape-changing polymeric materials have gained significant attention in the field of bioinspired soft robotics. However, challenges remain in versatilizing the shape-morphing process to suit different tasks and environments, and in designing systems that combine reversible actuation and self-healing ability. Here, we report halogen-bonded liquid crystal elastomers (LCEs) that can be arbitrarily shape-programmed and that self-heal under mild thermal or photothermal stimulation. We incorporate halogen-bond-donating diiodotetrafluorobenzene molecules as dynamic supramolecular crosslinks into the LCEs and show that these relatively weak crosslinks are pertinent for their mechanical programming and self-healing. Utilizing the halogen-bonded LCEs, we demonstrate proof-of-concept soft robotic motions such as crawling and rolling with programmed velocities. Our results showcase halogen bonding as a promising, yet unexplored tool for the preparation of smart supramolecular constructs for the development of advanced soft actuators.     

Quadruple H-Bonding and Polyrotaxanes Dual Cross-linking Supramolecular Elastomer for High Toughness and Self-healing Conductors

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 Transformable and Bulky Methacrylate Monomer That Enables the Synthesis of an MMA-nBA Alternating Copolymer: Sequence-Dependent Self-Healing Properties

In this study, we designed a methacrylate molecule with an alkyl-substituted trichloro salicylic acid pendant as a transformable bulky monomer to enable the synthesis of an alternating copolymer of methyl methacrylate (MMA) and n-butyl acrylate (nBA). The adamantyl-substituted methacrylate monomer ( 1-Ad ) showed very low homopolymerization propensity in radical polymerizations, but afforded the alternating copolymer with nBA via copolymerization. The 1-Ad units in the resultant copolymer were quantitatively and selectively transformed into MMA via transesterification with methanol to yield the alternating copolymer of MMA and nBA. Its alternating sequence was clearly demonstrated by a structural analysis via ¹³C NMR spectroscopy as well as the low reactivity ratios for the 1-Ad and nBA pair. Finally, we verified the superior self-healing ability of the alternating copolymer compared to that of the corresponding 1 : 1 statistical copolymer.     

Photoswitchable and Reversible Fluorescent Eutectogels for Conformal Information Encryption

Smart fluorescent materials that can respond to environmental stimuli are of great importance in the fields of information encryption and anti-counterfeiting. However, traditional fluorescent materials usually face problems such as lack of tunable fluorescence and insufficient surface-adaptive adhesion, hindering their practical applications. Herein, inspired by the glowing sucker octopus, we present a novel strategy to fabricate a reversible fluorescent eutectogel with high transparency, adhesive and self-healing performance for conformal information encryption and anti-counterfeiting. Using anthracene as luminescent unit, the eutectogel exhibits photoswitchable fluorescence and can therefore be reversibly written/erased with patterns by non-contact stimulation. Additionally, different from mechanically irreversible adhesion via glue, the eutectogel can adhere to various irregular substrates over a wide temperature range (−20 to 65 °C) and conformally deform more than 1000 times without peeling off. Furthermore, by exploiting surface-adaptive adhesion, high transparency and good stretchability of the eutectogel, dual encryption can be achieved under UV and stretching conditions to further improve the security level. This study should provide a promising strategy for the future development of advanced intelligent anti-counterfeiting materials.     

Dynamic Hydrogen-Bond Network as a Modulator of Bismuth–Antimony Complex Anodes for Self-Healable and Wider Temperature Adaptive Potassium Ion Batteries

Antimony (Sb)-based anodes are attractive candidates in potassium-ion batteries (PIBs) due to their superior capacities and rational potassium inserting voltages. However, the sluggish kinetics and poor interface compatibility severely hinder practical application. Herein, Bi_0.67Sb_1.33S₃ nanospheres embedded into in situ formed poly(3,4-ethylenedioxythiophene) crosslinked with polythioctic acid (PET@PTA) (Bi_0.67Sb_1.33S₃/PET@PTA) were elaborately conceptualized with hydrogen bonds exchangeable binding (HBEB) sites. Bi_0.67Sb_1.33S₃/PET@PTA exhibits notable self-healing ability and wider temperature adaptability. Bi_0.67Sb_1.33S₃/PET@PTA displays an impressive capacity of 819 mAh g⁻¹ at 0.05 A g⁻¹, prominent cycle ability with a 73 % capacity conservation after 500 cycles at 2 A g⁻¹, and high capacity retention of 66 % and 84 % at −40 and 70 °C to that case at room temperature, respectively, for potassium storage. This work provides a new perspective for HBEB sites in maximizing the desirable K⁺ storage performance.     

Strong,Supertough and Self-Healing Biomimetic Layered Nanocomposites Enabled by Reversible Interfacial Polymer Chain Sliding

Despite the remarkable progress in ultrastrong mechanical laminate materials, the simultaneous achievement of toughness, stretchability and self-healing properties in biomimetic layered nanocomposites remains a great challenge due to the intrinsic limitations of their hard essences and lack of effective stress transfer at the organic-inorganic fragile boundary. Here, an ultratough nanocomposite laminate is prepared by constructing chain-sliding cross-linking at the interface between sulfonated graphene nanosheets and polyurethane layers based on the ring molecules sliding on the linear polymer chains to release stresses. Unlike traditional supramolecular bonding toughening with limited sliding spacing, our strategy enables interfacial molecular chains reversible slippage when the inorganic nanosheets bear stretching force, providing sufficient interlayer spatial distance for relative sliding to dissipate more energy. The resulting laminates exhibit strong strength (22.33 MPa), supertoughness (219.08 MJ m⁻³), ultrahigh stretchability (>1900 %) and self-healing ability (99.7 %), which far surpass most of reported synthetic and natural laminate materials. Moreover, the fabricated proof-of-concept electronic skin shows excellent flexibility, sensitivity and healability for human physiological signals monitoring. This strategy breaks through the challenge that traditional layered nanocomposites are intrinsically stiff and opens up the functional application of layered nanocomposites in flexible devices.     

Hydrogel-Based Macroscopic Click Chemistry

The click reaction has found good utility across various fields due to the characteristics of high efficiency, atom economy, simple and mild reaction conditions. Click chemistry is usually utilized for connecting components of microscopic level, while it is still unable for joining macroscopic building blocks. Materials consisting of macroscopic building blocks realize the flexible fabrication of three-dimensional structures at macroscopic level, exerting significance on parallel manufactures. In this work, we reported macroscopic click chemistry utilizing hydrogel as macroscopic building blocks. Hydrogels G1 and G2 were prepared by incorporating M1 (N,N′-dimethyl-1,2-ethanediamine) and P1 (alkyne functionalized polyethylene glycol) respectively, where polymer chains formed through diffusion-induced amino-yne click reaction entangled different hydrogel networks together. Additionally, chain-like aggregates and complicated 3D structures such as tetrahedron and quadrangular pyramid were constructed based on the adhesion of the hydrogel blocks. The approach enables us to find more possibilities in the delicate designation of 3D aggregations as well as large-scale manufacturing.