Biomacromolecules, Vol.12, No.10, 3708-3714, 2011
Effects of pH and Salt Concentration on the Formation and Properties of Chitosan-Cellulose Nanocrystal Polyelectrolyte-Macroion Complexes
This study examines the effects of pH and salt concentration on the formation and properties of chitosan-cellulose nanocrystal (CNC) polyelectrolyte-macroion complexes (PMCs). The components' pK values, determined by potentiometric titration, were 6.40 for chitosan and 2.46 for the CNCs. The turbidity of PMC particle suspensions was measured as a function of chitosan-CNC ratio, pH, and salt concentration. The maximum turbidity values in titrations of a chitosan solution with a CNC suspension and vice versa occurred at charge ratios of 0.47 +/- 0.11 (SO3-/NH3+) and 1.16 +/- 0.06 (NH3+/SO3-), respectively. A pH increase caused a turbidity decrease due to shrinlring of the PMC particles upon changes in their components' degrees of ionization. An increase in salt concentration caused a decrease in turbidity due to charge-screening-related shrinking of the PMC particles. The effects of pH and salt concentration on particle size were confirmed by scanning electron microscopy.