Effect of Ionic Surfactants on the Viscoelastic Properties of Chiral Nematic Cellulose Nanocrystal Suspensions.

The gelation of cellulose nanocrystal (CNC) suspensions is explored in the presence of two ionic surfactants, namely, sodium dodecyl sulfate (SDS) with a negatively charged head and cetyltrimethylammonium bromide (CTAB) with a positively charged head. The viscosity profile of pure CNC suspensions indicated that at concentrations greater than 5 wt %, they exhibit gel-like behavior, where the viscosity shows a single shear-thinning profile. However, at concentrations lower than 1 wt %, the suspension shows isotropic behavior and experiences a transition to chiral nematic biphasic domains at increasing CNC concentration.