Molecular Dynamics of Drying‐Induced Structural Transformations in a Single Nanocellulose

Abstract

Nanocellulose is attracting attention in the field of materials science as a sustainable building block. Nanocellulose‐based materials, such as films, membranes, and foams, are fabricated by drying colloidal dispersions. However, little is known about how the structure of a single nanocellulose changes during the complex drying process. Here, all‐atom molecular dynamics simulations and atomic force microscopy is used to investigate the structural dynamics of single nanocellulose during drying. It is found that the twist morphology of the nanocellulose became localized along the fibril axis during the final stage of the drying process. Moreover, it is shown that conformational changes at C6 hydroxymethyl groups and glycoside bond is accompanied by the twist localization, indicating that the increase in the crystallinity occurred in the process. It is expected that the results will provide molecular insights into nanocellulose structures in material processing, which is helpful for the design of materials with advanced functionalities.

Morphological Changes of Polymer-Grafted Nanocellulose during a Drying Process

“…After the adsorption, the polymer chains were located on both sides of the core CNF and the polymer-grafted CNF exhibited a multimodal height distribution in the cross section (Figure d). Interestingly, the twist of the CNF in the core was relaxed in the course of the adsorption, and the twist angle of the core CNF along the fibril axis (θ twist ) decreased to ∼0.2 °/nm in the final structure (Figure g), while it has been reported that CNFs without surface grafting possess a twisted structure on the mica surface in an MD simulation . These results suggest the polymer brush layer on the both sides of the CNF physically relaxed the twisted structure of the CNF core during the adsorption.…”

“…Interestingly, the twist of the CNF in the core was relaxed in the course of the adsorption, and the twist angle of the core CNF along the fibril axis (θ twist ) decreased to ∼0.2 °/nm in the final structure (Figure 2g), while it has been reported that CNFs without surface grafting possess a twisted structure on the mica surface in an MD simulation. 71 These results suggest the polymer brush layer on the both sides of the CNF physically relaxed the twisted structure of the CNF core during the adsorption. The morphology at the water−mica interface was confirmed by in-liquid AFM observation (Figure 3b).…”