Ultrastretchable and Antifreezing Double-Cross-Linked Cellulose Ionic Hydrogels with High Strain Sensitivity under a Broad Range of Temperature

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 (similar to 236% of tensile strain) and high compressibility (similar to 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 similar to 100%) at -24 degrees C but also surprisingly transform into high visual transparency under a wide range of low temperature (-30 to -16 degrees 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.