Multifunctional nanocrystalline cellulose ionogels toward tough and sustainable materials

Design and fabrication of sustainable cellulose-based ionogels with good mechanical properties have attracted increasing research interest; however, most current developed ionogels show limited processibility and functionality. Here, we report the development of tough and multifunctional ionogels by mixing nanocrystalline cellulose (NCC) into ionic liquid (IL), where the partial solvation of NCCs enables the formation of ionogels with varied NCC loadings. Partially solvated NCCs (PS-NCCs) have high-crystallinity domains offering rigidity, surrounded by cellulose chains enabling flexibility and energy dissipation. The NCC ionogel can achieve a high Young's modulus (-44 MPa), toughness (-34 kJ m-2), and stretchability (-870% strain), while also exhibiting thermal-triggered self-healing, stiffness transition, shape memory, and conductivity-changing properties. The NCC ionogels show their potential to work as multi-functional platforms for advanced applications, including grippers, temperature sensors, and three-dimensional printing. In addition, the IL in the ionogel is recyclable, and the ionogel can be degraded in natural environmental conditions, further enhancing its sustainability.