Colloidal stability of negatively charged cellulose nanocrystalline in aqueous systems

Colloidal stability of negatively charged cellulose nanocrystalline (CNC) in the presence of inorganic and organic electrolytes was investigated by means of dynamic light scattering and atomic force microscopy. CNC could be well dispersed in distilled water due to the electrostatic repulsion among negatively charged sulfate ester groups. Increasing the concentration of inorganic cation ions (Na+ and Ca2+) resulted in CNC aggregation. CNC in divalent cation ion Ca2+ solution exhibited less stability than that in monovalent cation ion Na+ solution. Organic low-molecular-weight electrolyte sodium dodecyl sulfate (SDS) favored the stability of CNC suspension, whereas organic high-molecular-weight electrolyte sodium carboxymethyl cellulose (CMC) induced CNC particle aggregation due to intermolecular bridging interaction or entanglement. Cationic polyacrylamide (CPAM) caused a serious aggregation of CNC particles even at low concentration of CPAM. At low ionic strength (Na+, 1 mM), CNC were stable in aqueous solution at the pH range of 2–11.