Porous network structures composed of TEMPO-oxidized cellulose nanofibers(TOCNs) were successfully built up by a simple drying technique in air or oven where aqueous TOCN dispersions were dried on porous supports with mcron or submicron pores. A small amount of cationic surfactant was added to the TOCN dispersion to make hydrophilic TOCN surfaces hydrophobic to some extent. The porous TOCN networks formed inside the individual pores of the support had two-dimensional structures composed both of single and bundled TOCNs. Laser scanning microscopy was subjected to in situ monitoring during the formation of porous TOCN networks, showing that the wet thin films were first formed from the TOCN dispersion, followed by the gradual formation of submicron-sized pores in the films as water evaporated. The new method described here has potential for mass production of functional porous materials from cellulose nanofibers.
