It is a challenge to synthesize all-in-one molecular networks that are autonomously self-healable over a wide temperature range (from subzero to high), transparent, stretchable, and conductive. Here we demonstrate the fabrication of selfhealing, transparent, conductive, and highly stretchable elastomers by a photoinitiated copolymerization of two polymerizable deep eutectic solvent (PDES) monomers, acrylic amide (AAm)/choline chloride (ChCl) and maleic acid (MA)/ChCl type PDESs. Hydrogen bonds between binary building blocks of the poly-(AAm/ChCl-co-MA/ChCl) system can readily break and reform, allowing such all organic designed elastomers to self-heal over a wide temperature ranging from −23 to 60 °C while keep a highly transparent appearance. The hypermolecular network elastomers showed a fast self-healing property (within 2 s) without any other external stimuli and excellent self-healing efficiency (up to 94%). The elastomers were highly transparent (an average transmittance of 95.1%), intrinsically conductive (an ionic conductivity of 4.0 × 10 −4 S cm −1 ), and stretchable (strains up to 450%) at room temperature. We hypothesize that this behavior will find their potential use in display and/or optically related fields of stretchable electronics in harsh environments.

Stretchable and compressible hydrogels based on natural polymers have received immense considerations for electronics. The feasibility of using pure natural polymer-based hydrogels could be improved if their mechanical behaviors satisfy the requirements of practical applications. Herein, we report highly stretchable (tensile strain ∼126%) and compressible (compression strain ∼80%) cellulose ionic hydrogels (CIHs) among pure natural polymer-based hydrogels including cellulose, chitin, and chitosan via chemical cross-linking based on free radical polymerization of allyl cellulose in NaOH/urea aqueous solution. In addition, the hydrogels have good transparency (transmittance of ∼89% at 550 nm) and ionic conductivity (∼0.16 mS cm–1) and can be worked at −20 °C without freezing and visual loss of transparency. Moreover, the CIHs can serve as reliable and stable strain sensors and have been successfully used to monitor human activities. Significantly, the various properties of hydrogel can be controlled through rationally adjusting the chemically cross-linked density. Our methodology will prove useful in developing the satisfied mechanical and transparent CIHs for a myriad of applications in flexible electronics.

3D patternable, transparent, stretchable, and conductive elastomers based on the photopolymerization of the acrylic-acid/choline-chloride deep eutectic solvent were prepared, which can serve as flexible tactile/strain sensors.

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Stretchable and antifreezing conductive hydrogels, especially prepared from natural polymers, are beneficial for important and rapidly growing stretchable electronic devices. Unfortunately, the potential value of the pure natural polymer-based hydrogel in such applications is very limited because of its poor mechanical behavior and inevitable freeze of water-based hydrogels at subzero temperatures. Herein, we report the ultrastretchable and antifreezing double-cross-linked cellulose ionic hydrogels (DCIHs) prepared by ammonium persulfate initiating free radical polymerization of allyl cellulose and by NaCl inducing physical cross-linking. The acquired hydrogels display ultrastretchability (∼236% of tensile strain) and high compressibility (∼82% of compression strain) among pure polysaccharide-based hydrogels including cellulose, chitosan, and chitin. Simultaneously the soaking strategy in saturated NaCl solution also endows the DCIHs with excellent antifreezing properties that not only have good stretchability (strain up to ∼100%) at −24 °C but also surprisingly transform into high visual transparency under a wide range of low temperature (−30 to −16 °C). In addition, the DCIH with high reliability, response speed, as well as wide range strain sensor is also demonstrated by investigating the output electrical signals, showing the potential for applications in flexible electronics under a broad range of temperature.