  Cellulose ethers represent a class of water-soluble polymers widely utilized
across diverse sectors, spanning from healthcare to the construction industry.
This experimental study specifically delves into aqueous suspensions of
carboxymethylcellulose (CMC), a polymer that undergoes gel formation in acidic
environments due to attractive interactions between hydrophobic patches along
its molecular chain. We use rheometry to determine the linear viscoelastic
properties of both CMC suspensions and acid-induced gels at various
temperatures. Then, applying the time-temperature superposition principle, we
construct master curves for the viscoelastic spectra, effectively described by
fractional models. The horizontal shift factors exhibit an Arrhenius-like
temperature dependence, allowing us to extract activation energies compatible
with hydrophobic interactions. Furthermore, we show that acid-induced CMC gels
are physical gels that display a reversible yielding transition under external
shear. In particular, we discuss the influence of pH on the non-linear
viscoelastic response under large-amplitude oscillatory shear. Overall, our
results offer a comprehensive description of the linear and non-linear
rheological properties of a compelling case of physical hydrogel involving
hydrophobic interactions.
