title: Nanostructural reorganization of bacterial cellulose by ultrasonic treatment.
abstract: In this work, bacterial cellulose was subjected to a high-power ultrasonic treatment for different time intervals. The morphological analysis, scanning electron microscopy, and atomic force microscopy revealed that this treatment changed the width and height of the microfibrillar ribbons and roughness of their surface, originating films with new nanostructures. Differential thermal analysis showed a higher thermal stability for ultrasonicated samples with a pyrolysis onset temperature of 208 degrees C for native bacterial cellulose and 250 and 268 degrees C for the modified samples. The small-angle X-ray scattering experiments demonstrated that the treatment with ultrasound increased the thickness of the ribbons, while wide-angle X-ray scattering experiments demonstrated that the average crystallite dimension and the degree of crystallinity also increased. A model is proposed where the thicker ribbons and crystallites result from the fusion of neighboring ribbons due to cavitation effects.
authors.affiliation: Laboratório de Biopolímeros, Universidade Federal do Paraná, Caixa Postal 19081, 81531-990, Curitiba, Paraná, Brazil. paula.tischer@pq.cnpq.br
authors.forename: Paula C S Faria
authors.initials: PC
authors.lastname: Tischer
authors.forename: Maria Rita
authors.initials: MR
authors.lastname: Sierakowski
authors.forename: Harry
authors.initials: H
authors.lastname: Westfahl
authors.forename: Cesar Augusto
authors.initials: CA
authors.lastname: Tischer
mesh_terms: D001419:Bacteria / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D049329:Nanostructures; D012542:Scattering, Radiation; D014465:Ultrasonics
chemical_list: D002482:Cellulose