From micro to macro: modulating the properties of cationic lamellar phases with nanocelluloses

Cellulose-based nanomaterials have potential to act as renewable and versatile additives for tailoring properties of aqueous surfactant systems. This study compares the effect of negatively charged cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), and their molecular counterpart, carboxymethylcellulose (CMC), on the rheological properties and microstructural organization of aqueous aggregates of cationic di(hydrogenated tallow) dimethylammonium chloride. Their lamellar phases can be assumed as representative of those found in cosmetics, fabric softeners, and related formulations.

Samples were prepared with an excess of cationic surfactant relative to the anionic additives while maintaining a constant surfactant/additive mass ratio for both surfactant concentrations. The surfactant was slowly added to pre-existing (nano)cellulose suspensions or solutions, allowing lamellar phase formation to occur in the presence of nanoparticles or polymer chains. Rheological measurements were performed alongside differential scanning calorimetry, small- and wide-angle X-ray scattering experiments.

The rigidity and yield stress of the samples depend on the type of additive (CNC, CNF, or CMC) and the surfactant/additive ratio. With CNC, these properties increase with concentration, reaching a maximum at a surfactant/additive ratio of 100 (0.05 and 0.1 wt% CNC for 5 and 10 wt% surfactant, respectively), and then decrease at higher additive contents. The rheological behavior is closely linked to changes in lamellar organization, including variations in bilayer repeat distance and the coexistence of multiple lamellar phases in samples with CMC. These findings reveal the general colloidal outcome of hybrid oppositely charged lamellar-particle networks in aqueous surfactant systems, opening new opportunities for exploiting cellulose nanomaterials in concentrated surfactant formulations.