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.