Intrinsic viscosity of suspensions of electrosterically stabilized nanocrystals of cellulose

Electrosterically stabilized nanocrystals of cellulose (ENCCs) have emerged recently as new cellulose nanoparticles among common nanocrystals of cellulose (NCCs) and cellulose nanofibers. ENCC has a special structure being composed of a crystal with protruded amorphous chains at each endcaps bearing carboxyl groups. Here, we studied the intrinsic viscosity of aqueous suspensions of ENCCs as a function of pH and ionic strength. Low pH or high ionic strength reduced the ENCCs to rigid rod-like particles while a polyelectrolyte-like behavior was observed for suspensions of ENCCs around pH 7 and at low ionic strength. The pH had a great effect on charges due to both deprotonation of carboxyl groups and counter-ion effect, while the ionic strength only affected the surface charges of the particles. The zeta potential of ENCC suspensions was measured as a function of pH and ionic strength to establish a link between particle charges and the intrinsic viscosity. Finally, the Fedors model was used to compare our data in the case of rigid rod-like body behavior with literature data on NCC suspensions and the model was shown to be unsuitable.