Abstract
Cellulose nanofiber, which is one of biomass materials, attracts attention as a novel polymer material in recent years. It consists of multiple cellulose microfibril (CMF) forming a hierarchical structure. In this study, we evaluate the mechanical properties of a single CMF and two CMFs as a hierarchical structure, using All-Atom model and molecular dynamics simulation. The effects of existence of water molecules are evaluated for a single CMF model in vacuum as well as the model in which water molecules are arranged. In the structural relaxation simulation in water, CMF shows initial twist larger than in vacuum. This is because hydrogen bonds named H02-O6, which are one kind of intramolecular hydrogen bonds, increase in water, but another intramolecular hydrogen bonds, H03-O5, decrease there, as compared with results in vacuum. In the torsion simulation of a single CMF, it is observed that the initial twist generated during the structural relaxation simulation leads to the anisotropy of rigidity depending on the torsion direction. In addition, the rigidity of a single CMF increases in water. In the simulation of transmission of rotation by a hierarchical structure consisting of two CMFs, it is found that rotation is transferred by breaking the hydrogen bonds at the interface. Also, hydrogen bonds at the interface tends to decrease due to the effect of water molecules existing at the interface. Furthermore, in water, the ratio of transmission of the rotation angle is improved.
