Characterization of an Amphiphilic Janus-Type Surface in the Cellulose Nanofibril Prepared by Aqueous Counter Collision

Abstract

Cellulose nanofibrils, which attract extensive attention as a bio-based, sustainable, high-performance nanofibril, are believed to be predominantly hydrophilic. This study aimed to prove the presence of an amphiphilic “Janus-type fiber surface” in water with hydrophobic and hydrophilic faces in a cellulose nanofibril (ACC-CNF) that was prepared by the aqueous counter collision method. We clarified the surface characteristics of the ACC-CNF by confocal laser scanning microscopy with a carbohydrate-binding module and congo red probes for the hydrophobic planes on the cellulose fiber surfaces and calcofluor white as hydrophilic plane probes. The results indicated the presence of both characteristic planes on a single ACC-CNF surface, which verifies an amphiphilic Janus-type structure. Both hydrophobic probes adsorbed onto ACC-CNFs for the quantitative evaluation of the degree of ACC-CNF surface hydrophobicity by Langmuir’s adsorption theory based on the optimal maximum adsorption amounts for various starting raw material types.

Covering Soybean Leaves With Cellulose Nanofiber Changes Leaf Surface Hydrophobicity and Confers Resistance Against Phakopsora pachyrhizi

“…We demonstrated that ASR was suppressed by CNF made from the ACC method (Figures 1A,B). Various preparation methods have been proposed including mechanical and chemical processes (Tsuji et al, 2021). CNF made from the ACC method has both hydrophobic and hydrophilic sites resulting in amphiphilic properties (Kondo et al, 2014).…”

Cellulose Nanofibrils Pulverized from Biomass Resources: Past, Present, and Future Perspectives

“…2 and 3, the nanocellulose surface obtained by TEMPO oxidation and the grinder method exhibit high hydrophilicity similar to that of conventional natural cellulose fibers. In contrast, the nanocellulose surface obtained by the ACC method is more hydrophobic and amphiphilic (Kondo and Kasai, 2015;Tsuboi et al, 2014;Tsuji et al, 2021).…”

“…3B). The resulting ACC-CNFs have a Janus-type amphiphilic surface composed of both hydrophobic and hydrophilic planes in an aqueous system (Tsuji et al, 2021). Kose et al (2011c) reported that ACC provides a single CNF from bacterial nanocellulose (BNC) pellicles, denoted ACC-BNC herein, which are nanofibers engaged in a 3D network secreted by Gluconacetobacter bacteria, that exhibited amphiphilic Fig.…”

“…Recently, the ACC method afforded CNFs with different surface properties from various cellulosic raw materials comprising different hierarchical structures depending on the species present, as described later (Tsuji et al, 2021).…”

“…ACC-CNFs are likely to exhibit specific phenomena owing to their two anisotropic faces in aqueous media (Tsuji et al, 2021). Kose et al (2011a) reported that the wettability of solid substrates, regardless of whether the surface was hydrophilic or hydrophobic, can be switched by spray-coating with ACC-CNFs.…”