Hierarchically constructing hyperelastic and waterproof bacterial cellulose/PMSQ/boehmite composite aerogels for superhigh flame retardancy and ultralow thermal conductivity

Biomass-based cellulose aerogels show great potential in many important functional applications, particularly in the field of thermal insulation. However, it has been a grand challenge to construct multifunctional cellulose aerogels with hyperplastic, flame retardancy, and superhydrophobicity for enabling effective thermal insulation in practical application. Here, a hierarchically construction strategy for fabricating cellulose composite aerogels by co-assembling PMSQ-coated BC nanofibers and boehmite sol during directional freezing technique and a silanization process followed by PDMS chemical vapor deposition is reported. Besides, PCB composite aerogels exhibit low bulk density (17.8 mg·cm −3 ) and high specific surface area (223.9 m 2 ·g −1 ) and excellent thermal insulation (low thermal conductivity of 25.7 mW·m −1 ·K −1 ). Remarkably, its super-elasticity (recovers quickly after being subjected to a pressure of 9000 times its own weight) is realized by the created “beam-column” structural design. Owing to the presence of the synergistic effect of PMSQ and boehmite, PCB composite aerogels possess an ultra-high LOI value of 58 and rapidly self-extinguishes upon removal from fire. Notably, the PDMS after graft modification by via CVD imparts PCB superhydrophobicity, evidenced by a static WCA value of 151° ± 0.7°. This study offers a facile strategy for creating multifunctional cellulose aerogels with great potential for applications in thermal insulation, thermal management, and fire safety.