  We use time-resolved mechanical spectroscopy to offer a detailed picture of
the gelation dynamics of cellulose nanocrystal (CNC) suspensions following
shear cessation in the presence of salt. CNCs are charged, rodlike colloids
that self-assemble into various phases, including physical gels serving as soft
precursors for biosourced composites. Here, a series of linear viscoelastic
spectra acquired across the sol-gel transition of CNC suspensions are rescaled
onto two master curves, that correspond to a viscoelastic liquid state prior to
gelation and to a soft solid state after gelation. These two states are
separated by a critical gel point, where all rescaling parameters diverge in an
asymmetric fashion, yet with exponents that obey hyperscaling relations
consistent with previous works on isotropic colloids and polymer gels. Upon
varying the salt content, we further show that these critical-like dynamics
result in both time-connectivity and time-concentration superposition
principles.
