title: Hydrophobic, ductile, and transparent nanocellulose films with quaternary alkylammonium carboxylates on nanofibril surfaces.
abstract: Hydrophobic, ductile, and transparent nanocellulose films were prepared by casting and drying aqueous dispersions of 2,2,6,6-tetramethylpiperidine-1-oxyl-oxidized cellulose nanofibrils (TOCNs) with quaternary alkylammoniums (QAs) as counterions for the surface carboxylate groups. TOCN films with tetramethylammonium and tetraethylammonium carboxylates showed high optical transparencies, strain-to-failure values (14-22%), and work-of-fracture values (20-27 MJ m(-3)). The ductility of these films was likely caused by the alkyl chains of the QA groups densely covering the TOCN surfaces and being present at the interfaces between the TOCN elements in the films. The water contact angle of the TOCN-QA films increased to ∼100° by introducing tetra(n-butyl)ammonium groups as counterions. Thus, TOCN film properties can be controlled by changing the chemical structure of the counterions from Na to QAs. The hydrophilic TOCN surfaces can be changed to hydrophobic simply and efficiently by the conversion from TOCN-Na to TOCN-QA, when TOCNs are used as nanofillers in hydrophobic polymer matrices.
authors.affiliation: Department of Biomaterials Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo , Tokyo 113-8657, Japan.
authors.forename: Michiko
authors.initials: M
authors.lastname: Shimizu
authors.forename: Tsuguyuki
authors.initials: T
authors.lastname: Saito
authors.forename: Hayaka
authors.initials: H
authors.lastname: Fukuzumi
authors.forename: Akira
authors.initials: A
authors.lastname: Isogai
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry* / Q000378:metabolism; D002482:Cellulose / Q000737:chemistry* / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D057139:Nanofibers / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry* / Q000378:metabolism; D013499:Surface Properties; D013718:Tensile Strength / Q000502:physiology
chemical_list: D002264:Carboxylic Acids; D000644:Quaternary Ammonium Compounds; D002482:Cellulose; C027917:tetramethylammonium