Negative Poisson's ratio structural cellulose aerogel with excellent impact resistance

Cellulose aerogel is a promising cushioning material for impact-resistant applications owing to its low density and high porosity. However, the weakness of mechanical strength and stress dispersion effects resulted in local damage and failure of aerogels. Herein, we constructed significantly negative Poisson's ratio effect of nanocellulose aerogels by covalently cross-linking cellulose nanofibers (CNF) and polyacrylamide (PAM), and introducing concave hexagonal structure. The nanocellulose aerogels with concave hexagonal exhibited an anisotropic negative Poisson's ratio (maximum negative Poisson's ratio of -0.203), providing high energyabsorbing efficiency and large deformation buffer space. During compression, the crosslinked networks formed within the CNF/PAM cellular walls act as strain transfer channels, further improving the strain conductivity and the mechanical strength of the nanocellulose aerogels. The negative Poisson's ratio structure and dense cellular walls provided the aerogel excellent stress dispersion and energy-absorbing effects at 30% strain, and excellent impact-resistant properties under the strong impact of a steel ball. This work provides an attractive strategy to construct aerogels with eco-friendly, lightweight, higher strength, and negative Poisson's ratio structure and extend the applications in the field of impact energy-absorbing and cushioning, i.e., aeronautics, high speed vehicle, and packaging machinery.