Designing High-Strength, Sustainable Cellulose Ionogels by Optimization of Fiber Structure and Molecular Weight

Cellulose, as a natural polymer material with unique renewability, biocompatibility, and biodegradability, has made significant advancements for the sustainable and promising ionogel. However, the cellulose ionogel, a gel matrix composed of cellulose and ionic liquids (ILs), suffers from weak mechanical strength. Herein, this study proposes a method for optimizing the fiber structure and molecular weight of cellulose (structural engineering). Such engineered cellulose fiber (MF, medium-length fibers) with optimized fiber length and specific surface area demonstrates excellent dissolution behavior, followed by forming strong hydrogen bonds between cellulose molecules, which is beneficial for improving the mechanical strength of the resultant cellulose ionogel. Synchronously, the MF with a relatively high molecular weight indeed supports superior mechanical performance due to the stable entanglement network of large cellulose molecules. As a result, our MF-based cellulose ionogel enables an exceptional tensile strength of 3.5 MPa and a Young’s modulus of 5.8 MPa, much higher than that of the original fiber-based ionogel. In addition, the prepared MF cellulose ionogel also features a high ionic conductivity (69 mS/cm), which makes it a high-performance sensor with a sensitivity of 8. The proposed structural engineering strategy facilitates the development of high-strength macromolecule-based ionogels beyond cellulose for constructing high-performance, sustainable ionogels toward next-generation smart materials.