Colloidal stability of chitin nanofibers in aqueous systems: Effect of pH, ionic strength, temperature & concentration

Chitin nanofibers are emerging as a very attractive bio-compatible material in number of advanced materials applications. In this work, the colloidal stability of the chitin nanofibers was investigated against pH, ionic strength, temperature and concentration. Aqueous solutions of chitin nanofibers were found to be stabilized due to the carboxylic acid moieties available in the fibril surface as evidenced by both C-13 NMR and potentiometric titration methods. Amongst others, pH and ionic strength were the most influential factors which determine both hydrodynamic diameter and zeta potential. The chitin nanofiber dispersions were stabilized at pH values higher than 7, with an average zeta potential value of -22.5 mV. A monotonic increase of zeta potential was observed with respect to increase in ionic strength. Zeta potential got stabilized at -14.0 mV for ionic strengths over 20 mM of NaCl. Hydrodynamic particle size was also found to be a function of temperature and concentration.