Acid-induced gelation of carboxymethylcellulose solutions

TL;DR

This study comprehensively characterizes acid-induced gelation in carboxymethylcellulose, revealing microstructural self-similarity, a superposition principle, and a mean-field model, with experimental validation from neutron scattering and NMR.

Contribution

It introduces a unified phase diagram, a superposition principle for viscoelastic spectra, and a mean-field model for CMC gelation, supported by multiple experimental techniques.

Findings

CMC gels exhibit power-law viscoelastic spectra

Neutron scattering shows fibrous network structure

NMR signatures reveal gelation process

Abstract

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.