title: Effects of pH and salt concentration on the formation and properties of chitosan-cellulose nanocrystal polyelectrolyte-macroion complexes.
abstract: 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 (SO(3)(-)/NH(3)(+)) and 1.16 ± 0.06 (NH(3)(+)/SO(3)(-)), respectively. A pH increase caused a turbidity decrease due to shrinking 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.
authors.affiliation: Macromolecules and Interfaces Institute, Department of Wood Science and Forest Products, Virginia Tech, Blacksburg, Virginia 24061, United States.
authors.forename: Hezhong
authors.initials: H
authors.lastname: Wang
authors.forename: Chen
authors.initials: C
authors.lastname: Qian
authors.forename: Maren
authors.initials: M
authors.lastname: Roman
mesh_terms: D000284:Administration, Oral; D001672:Biocompatible Materials / Q000032:analysis / Q000138:chemical synthesis*; D002482:Cellulose / Q000737:chemistry*; D048271:Chitosan / Q000737:chemistry*; D016503:Drug Delivery Systems / Q000379:methods*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D008970:Molecular Weight; D053758:Nanoparticles / Q000737:chemistry; D009391:Nephelometry and Turbidimetry; D010316:Particle Size; D011108:Polymers / Q000032:analysis / Q000737:chemistry*; D012492:Salts / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D012995:Solubility
chemical_list: D001672:Biocompatible Materials; D007477:Ions; D011108:Polymers; D012492:Salts; D012965:Sodium Chloride; D002482:Cellulose; D048271:Chitosan