Mid Sweden University

This work reveals the structural variations ofcellulose nanofibers (CNF) prepared from different cellulosesources, including softwood (Picea abies), hardwood (Euca-lyptus grandis × E. urophylla), and tunicate (Ciona intestinalis),using different preparation processes and their correlations tothe formation and performance of the films prepared from theCNF. Here, the CNF are prepared from wood chemical pulpsand tunicate isolated cellulose by an identical homogenizationtreatment subsequent to either an enzymatic hydrolysis or a2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxi-dation. They show a large structural diversity in terms ofchemical, morphological, and crystalline structure. Amongothers, the tunicate CNF consist of purer cellulose and have a degree of polymerization higher than that of wood CNF.Introduction of surface charges via the TEMPO-mediated oxidation is found to have significant impacts on the structure,morphology, optical, mechanical, thermal, and hydrophobic properties of the prepared films. For example, the film density isclosely related to the charge density of the used CNF, and the tensile stress of the films is correlated to the crystallinity index ofthe CNF. In turn, the CNF structure is determined by the cellulose sources and the preparation processes. This study providesuseful information and knowledge for understanding the importance of the raw material for the quality of CNF for various typesof applications.