Dispersion, stability and size measurements for cellulose nanocrystals by static multiple light scattering

Static multiple light scattering (SMLS) is used to provide qualitative information on cellulose nanocrystal (CNC) suspensions as a function of the methods used to disperse the dry CNCs and, in some cases, to estimate the equivalent size for primary particles and their aggregates. The methods were validated by measuring the mean diameter of several sizes and concentrations of silica particles which are approximately monodisperse and spherical, both of which significantly simplify the analysis of SMLS data. The results indicate that uncertainty in the silica density contributes to differences between the estimated SMLS diameters and those determined by dynamic light scattering. Suspension stability, sedimentation kinetics, and particle size as a function of dispersion method were evaluated for CNC suspensions by measuring the intensity profiles of light transmitted through the sample as a function of time, and applying sedimentation or light scattering theories. The results demonstrate that SMLS is a useful method for monitoring CNC dispersion for samples that are too concentrated to study by DLS. The sedimentation analysis provides qualitative information on the presence and size (equivalent diameter) of CNC aggregates/agglomerates and evidence for formation of a stable phase that forms during concurrent sedimentation and dispersion of CNC aggregates for unsonicated suspensions and is hypothesized to be a gel phase.