How nanocelluloses affect the microstructure and rheological properties of surfactant lamellar phases

Cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF) have been extensively studied as potential rheological modifiers in different products1. In this work, we investigated the structural and rheological properties of systems composed by CNC and CNF suspensions into lamellar phases of dioctadecyldimethylammonium bromide (DODAB), a double-chain cationic surfactant. The hybrid materials were prepared with surfactant concentrations in the range of 10 and 50 % w/w and CNC/CNF concentrations were fixed in 1 and 0.1 % w/w, respectively.
Amplitude sweeps showed higher values of storage (G’) than loss (G”) moduli for all shear rates applied. Both moduli increased with frequency as observed by frequency sweeps measurements. No significant changes were observed in the behavior and intensity of the amplitude and frequency sweeps after the addition of the nanocelluloses. Furthermore, flow curves revealed a viscoelastic behavior and the addition of nanocelluloses did not affect the zero shear viscosity values. For the hybrid materials, DSC analyses revealed minor changes at the transition temperature (Tm) associated with the Lβ to Lα lamellar phase transition. SAXS measurements showed a shift of the scattered peaks towards higher q values with the addition of nanocelluloses, which suggests smaller repeat distance of the bilayers.