Nonlinear viscoelastic characterization of charged cellulose nanocrystal network structure in the presence of salt in aqueous media

The change in ionic strength of cellulose nanocrystal (CNC) suspensions is shown to contribute to a respective change in colloidal behavior, such as stiffness and fractal gelation. In this study, dynamic colloidal behavior and stability of aqueous CNC suspensions and their correlation with nonlinear viscoelastic properties of the CNC gel structures in the presence of different concentrations of sodium chloride (NaCl) salt were investigated. The microstructure of CNC/salt suspensions/gels were investigated with a wide range of characterization technique. To obtain further insight into the network structure of CNC/salt systems, for the first time, nonlinear rheology of the suspensions/gels was analyzed to correlate macro-mechanical viscoelastic response of the CNC/salt aqueous systems to structural changes as a response to strain. The intra-cycle viscoelasticity, explained utilizing qualitative Lissajous–Bowditch plots and quantitative nonlinear parameters, demonstrates a strong dependence of the nonlinear response of the samples to salt concentration, CNC concentration, and frequency of deformation. Higher intra-cycle nonlinearity was observed upon increasing the salt loading. Graphic abstract