Aging dynamics and generalized superposition principles in carbon black-carboxymethylcellulose hydrogels
Year: 2026
Type: preprint
Abstract: Aqueous dispersions of hydrophobic carbon black (CB) particles can be stabilized by carboxymethylcellulose (CMC), forming CB-CMC hydrogels whose microstructure is controlled by the relative CB-to-polymer content. At low CMC content, CB particles form a percolated, electrically conductive network, whereas at higher polymer content, CB particles act as isolated physical crosslinkers within an electrically insulating polymer matrix [see Legrand \textit{et al.}, Macromolecules 56, 2298-2308 (2023)]. Combining rheology and electrical impedance spectroscopy, we show that these two regimes exhibit markedly different aging dynamics. Conductive hydrogels exhibit logarithmic elastic recovery associated with a percolated CB network, whereas insulating hydrogels exhibit a combination of logarithmic and power-law stiffening, accompanied by dielectric polarization associated with confined ionic motion. The insulating hydrogels further exhibit a time-aging superposition principle, as their viscoelastic spectra measured in a time-resolved fashion can collapse onto a single master curve. Under steady shear, the viscoelastic response measured perpendicular to the flow also obeys a time--shear-rate superposition principle. Remarkably, the scaling between the shift factors under shear is reminiscent of critical-gel behavior, unlike that observed during aging at rest. Finally, time-resolved rheo-USAXS measurements performed during shear-rate cycles reveal structural rearrangements of CB particles and clusters that correlate with rheological hysteresis. These results provide a microstructural basis for understanding the nonlinear rheology of insulating CB-CMC hydrogels and establish generalized superposition principles as a unifying framework for their aging and flow behavior.
Source: arXiv (Cornell University)
Institutions: École Normale Supérieure de Lyon, Centre National de la Recherche Scientifique, Laboratoire de Physique de l'ENS de Lyon, Ingenierie des Materiaux polymeres, Unité de Mathématiques Pures et Appliquées, Université Jean Monnet, Institut National des Sciences Appliquées de Lyon, Université Jean Monnet, Lyon 1 Université, KU Leuven
Language: English
Subfield: Fluid Flow and Transfer Processes
Field: Chemical Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223958510