With increasing environmental awareness and safety concerns, cellulosic materials have drawn considerable attention. Cellulose can be further extracted into its nanoforms to yield either fibrous or crystalline nanocellulose, both offering complex and versatile functionalities. Cellulose nanofibrils (CNFs) can be chemically modified by TEMPO radicals by selectively replacing hydroxyl groups with carboxylate groups. Such TEMPO-oxidized (TO)-CNF forms continuous self-standing films that are susceptible to swelling in the presence of water vapor. In this work, we investigated the swelling behavior and accompanying free-volume change of TO-CNF films prepared from different conditions: ultrasonication of TO-CNF suspension and film drying temperatures. Ultrasonication of TO-CNF suspension prior to film casting increased both the free-volume fraction and pore size but decreased the size of nanofibers, contributing to small change in swelling. Films drying temperatures unaffected the free-volume fraction and nanofibers size but decreased the free-volume pore size. In addition, film density increased with drying temperature and therefore reduced swelling capacity.

Free-volume characterization of TEMPO-oxidized cellulose nanofibrils films

256th National Meeting (2018)

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