  The present work offers a comprehensive description of the acid-induced
gelation of carboxymethylcellulose (CMC), a water-soluble derivative of
cellulose broadly used in numerous applications ranging from food packaging to
biomedical engineering. Linear viscoelastic properties measured at various pH
and CMC contents allow us to build a sol-gel phase diagram, and show that CMC
gels exhibit broad power-law viscoelastic spectra that can be rescaled onto a
master curve following a time-composition superposition principle. These
results demonstrate the microstructural self-similarity of CMC gels, and
inspire a mean-field model based on hydrophobic inter-chain association that
accounts for the sol-gel boundary over the entire range of CMC content under
study. Neutron scattering experiments further confirm this picture and suggest
that CMC gels comprise a fibrous network crosslinked by aggregates. Finally,
low-field NMR measurements offer an original signature of acid-induced gelation
from the solvent perspective. Altogether, these results open avenues for
precise manipulation and control of CMC-based hydrogels.
