Microfibril Straightening of Cotton Cellulose Promotes Mechanical Deterioration During Aging

The strength of cellulose materials can be affected by minor degradation during aging, with the underlying mechanisms remaining unclear. Here the evolution of cotton cellulose microfibril 3D structure during the aging process is investigated, using a combination of cryogenic electron tomography and other high‐resolution imaging techniques. The results reveal a coiled‐to‐straight transition of the microfibrils. This transition is closely associated with molecular chain scission and recrystallization of cellulose, and coincides with the mechanical failure of the material. Finite‐element simulations indicate that the straightening of the microfibrils lowers their defect tolerance and concentrates stress, which may play a key role in the loss of material strength upon the transition. These findings provide molecular‐to‐macroscopic insights into the degradation of cellulose, offering new perspectives for enhancing the durability of cellulose materials.