title: Engineered pigments based on iridescent cellulose nanocrystal films.
abstract: A simple method to produce biobased iridescent pigments from cellulose nanocrystal (CNC) films is reported. The process consists of forming nanostructured films from a CNC liquid-crystalline suspension and an appropriate dry grinding. The features of the iridescent pigments are described; they have a flake-like morphology with a thickness of 25 μm. However, because of the presence of sulfate groups, thermal degradation and high redispersion in water occur, which affect the iridescent property of these biobased pigments. To overcome such limitations, two post-treatments are proposed. The sulfate ester groups are removed from the iridescent pigments with vacuum overdrying. The mass loss of iridescent pigment in water is reduced with an increase of the ionic strength in the aqueous medium by NaCl addition. These post-treatments have proven to be efficient and engineered pigments based on CNC films can be used to add anticounterfeiting features to packaging manufactured by classical paper techniques or extrusion.
authors.affiliation: University of Grenoble Alpes, LGP2, F-38000 Grenoble, France; CNRS, LGP2, F-38000 Grenoble, France.
authors.forename: Raphael
authors.initials: R
authors.lastname: Bardet
authors.affiliation: Materials Characterization Center, Grenoble INP, Pagora 461, rue de la papeterie 38402, Saint-Martin-d'Hères, F-38000 Grenoble, France.
authors.forename: Francine
authors.initials: F
authors.lastname: Roussel
authors.affiliation: Materials Characterization Center, Grenoble INP, Pagora 461, rue de la papeterie 38402, Saint-Martin-d'Hères, F-38000 Grenoble, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Coindeau
authors.affiliation: University of Grenoble Alpes, LGP2, F-38000 Grenoble, France; CNRS, LGP2, F-38000 Grenoble, France.
authors.forename: Naceur
authors.initials: N
authors.lastname: Belgacem
authors.affiliation: University of Grenoble Alpes, LGP2, F-38000 Grenoble, France; CNRS, LGP2, F-38000 Grenoble, France. Electronic address: julien.bras@grenoble-inp.fr.
authors.forename: Julien
authors.initials: J
authors.lastname: Bras
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry; D055620:Optical Phenomena; D009994:Osmolar Concentration; D010858:Pigmentation; D014618:Vacuum; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D002482:Cellulose
keywords: Cellulose nanocrystals; Iridescence; Nanocellulose; Pigment grinding