title: Formation of nanosized islands of dialkyl β-ketoester bonds for efficient hydrophobization of a cellulose film surface.
abstract: The efficient hydrophobization mechanism of a hydrophilic cellulose film surface with alkylketene dimer (AKD) was studied in terms of formation of β-ketoester bonds at AKD/cellulose interfaces and their nanosized distribution analysis. AKD-treated cellulose and nanocellulose films were sequentially extracted with chloroform, hot water, and dioxane/water. Atomic force microscopy and high-resolution secondary-ion mass spectrometry were used to analyze the surface structures of the AKD-treated cellulose films and those after the sequential extraction. The results showed that the AKD molecules had melted and transformed into spherical nanoparticles, ∼37 nm in diameter, on the film surface during heat treatment, forming "sea/island"-like structures; the film surface projection area comprised 99% hydrophilic cellulose and 1% hydrophobic AKD nanoparticles. Determination of the AKD contents in the films revealed that an extremely small amount of AKD/cellulose β-ketoester bonds were likely to form at the AKD/cellulose interfaces during heating, clearly contributing to the hydrophobic nature of the sequentially extracted cellulose films.
authors.affiliation: Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo , 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Quanling
authors.initials: Q
authors.lastname: Yang
authors.forename: Miyuki
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Tsuguyuki
authors.initials: T
authors.lastname: Saito
authors.forename: Akira
authors.initials: A
authors.lastname: Isogai
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D004952:Esters / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008567:Membranes, Artificial
chemical_list: D004952:Esters; D008567:Membranes, Artificial; D002482:Cellulose