EXPERIMENTAL SECTION
initial CNCs solution was prepared by controlled sulfuric acid-catalyzed degradation of the bulk cellulose fibres, based on modification of previously reported procedures,38, experiment details given in the Supporting Information. Typically, 10 ml CNCs suspension (10 wt%) were injected into a 25 ml Teflon beaker and equilibrated for 6h. Then, freeze-casting was performed on a cold finger setup, as previously described.28 The beaker was put into a Cu cylinder disk, half of which was dipped into liquid nitrogen. The freezing process was visually assessed. Consequently, the CNCs suspension was directionally frozen from the bottom Cu/suspension interface to the top area until the water in suspension was totally frozen. Subsequently, the frozen composite was transferred to freeze drier, followed by sublimation of the ice at 0.6 mbar and room temperature for 24 h to obtain the CNCs aerogel. The obtained monolith was termed the LROC-1 aerogel.
In order to study the concentration-dependent self-assembly of CNC nanoparticles within ice crystal matrix, 10 ml of a 3 wt% CNCs suspension was employed as the initial precursor for freeze casting, performed using the same process. The obtained aerogel was labelled LROC-2.