Novel polymerized ionic liquids with different counterions were constructed, where ionic aggregations serve as physical cross-links providing excellent self-healing performance.

Perusing elastomers capable of self-healing offers new opportunities to enable next-generation flexible electronics, but remains greatly challenging; because, few of them can simultaneously possess desirable mechanical strength, elasticity, and self-healing efficiency. Herein, a dynamic dual-crosslinked networks strategy is employed to develop the elastomers via synthesis of ionic polymer catalyzed using the Grubbs's third-generation catalyst (G3) and subsequent ureido-pyrimidinone (UPy) grafting. Specifically, UPy exhibits a unique gradient distribution on ionic polymer chains. Large UPy clusters form in the dense UPy region with robust cross-links that can stabilize the system, while UPy dimers in sparse regions with weak ionic interactions can act as sacrificial bonds for energy dissipation. Therefore, the obtained elastomers exhibit superb mechanical properties with high stretchability (1900%), high toughness (33.8 MJ m −3 ), and excellent elasticity (>85%). Importantly, deactivated [Ru] = CHOEt complex (G3 derivative) is proved to have an inherently outstanding photothermal effect under near-infrared (NIR) irradiation. Benefiting from this feature, the elastomers achieve nearly complete self-healing within 4.5 min under NIR. Furthermore, the elastomers are employed as the base materials to construct flexible self-healing conductors with stable conductivity even being stretched to 1200%. This work exercises a profound influence on the rational design of high-performance self-healing elastomers.

Polymerized ionic liquids (PILs) represent one class of promising candidates for self-healing materials because of the potential diffusion of ion pairs from one aggregation to another. Therefore, dynamics of ionic aggregation plays the crucial role in the self-healing process. However, a win–win situation to both self-healing efficiency and mechanical strength is a major challenge for PILs and even all intrinsic healable materials. To resolve this challenge, a series of novel imidazolium-based norbornene PILs with fine-tuned side-chain microstructures were synthesized in the present work. The inserted imidazolium groups divide side chains into two parts: spacer and tail. By tuning the length of these two parts independently, self-healing efficiency of PILs could be significantly improved without sacrificing the mechanical strength. The increase in spacer segments by eight methylenes decreased the glass transition temperature by 70 °C and turned the PIL from a strong material into a highly stretchable material. It was very useful to find that tuning the lengths of spacer and tail conversely could achieve comparable mechanical strength. More importantly, our results revealed that long tail segments with 5, 7, or 9 methylenes formed an additional tail region between ionic aggregations, which remarkably reduced the average aggregation distance and consequently accelerates healing kinetics. The understanding on structure-healing interplay provides a convenient and efficient molecular design approach for optimizing mechanical strength and healing efficiency simultaneously.

Flexible photodetectors are fundamental elements to develop flexible/wearable systems, which can be widely used for in situ health and environmental monitoring, human-machine interacting, flexible displaying, etc. However, the degraded performance or even malfunction under severe mechanical deformation and/or damage remains a key challenge for current flexible photodetectors. In this article, a flexible photodetector is developed with strong self-healing capability and stable performance under large deformation. This photodetector is made of the 2D material self-healing film by mixing 2D materials homogenously with the self-healing polymer of imidazolium-based norbornene polymerized with ionic liquids and counterions. The 2D material self-healing films show enhanced light absorption, and thus, decent photoresponse as compared to the pure self-healing film. The achieved photoresponse remains stable and even increases under small tensile strain within 150%, while decreases slightly under large tensile strain up to 1000%. Moreover, the photodetector not only can be fully recovered from repeated mechanical cuttings, but also presents excellent long-term stability in ambient condition for 500 days without showing any obvious degraded performance. Furthermore, a large-area 2D material self-healing photodetection array is designed with adjustable pixel size, which successfully recognizes the patterns of "T", "J", and "U".

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