Design of a flexible cellulose framework via supramolecular structure modulation and its application in hydrogel...

Cellulose framework derived from wood has been widely used as reinforcement for high performance hydrogel sensors fabrication. However, due to the native brittleness of wood, the cellulose framework-reinforced hydrogels present mechanical rigidity, limiting their applications as wearable electronics. Herein, we report a time-dependent alkaline treatment strategy to modulate the supramolecular structure of cellulose frameworks. The effect of NaOH treatment duration was systematically investigated to identify an optimal cellulose framework (designated ADW4) that synergistically combines flexibility and mechanical strength. The optimized ADW4 exhibited a highly crystalline structure with superior mechanical properties, demonstrating a 17.1 % increase in tensile strength and a 140.1 % improvement in toughness over natural wood. Employing the obtained optimal cellulose framework as the reinforcement yielded a conductive hydrogel (PADW4-Li), which demonstrated dramatically improved mechanical strength (a 35,700 % increase compared to pure polyacrylamide (PAM)) and excellent ionic conductivity (3 mS cm^-1). The PADW4-Li hydrogel exhibits high utility, proving capable of not only monitoring physiological signals but also sensitively detecting minute deformations. The regulation of the supramolecular structure of the cellulose framework mediated by this alkali treatment endows it with both flexibility and mechanical strength, providing a new path for its use as the reinforcing phase of composite materials.