2.2. Chemical modification of the CNFsThe CNFs were acetylated using the method reported by Jonoobi,Harun, Mathew, Hussein et al. (2010) briefly as follows. Prior toacetylation, the aqueous suspension containing CNFs was extractedwith acetone and methanol (2:1 by volume) in a Soxhlet for 6 h.Then, the solvent exchanged from methanol to glacial acetic acidby centrifugation (three times). The extracted CNFs, acetylated inacetic anhydride (1:20 by weight) and 5 wt% pyridine as catalyst,were refluxed at 100◦C for 4 h. At the end of the reaction, the treatedCNFs were extracted using distilled water (2:1 by volume) for 6 hin order to remove un-reacted acetic anhydride and acetic acid by-products. Finally, four cycles of solvent exchange was performed bycentrifugation to obtain aqueous dispersions of acetylated CNFs.