Light Scattering Study of Chitosan in Acetic Acid Aqueous Solutions

Using intrinsic viscosity, static light scattering (SLS), and dynamic light scattering (DLS), we demonstrated that the particle sizes of chitosan molecules in dilute acetic acid/water solutions increased with decreasing pH value. SLS data also demonstrated that the second virial coefficient (A2) increased with decreasing pH value suggesting that solubility of chitosan in water increased with increasing acetic acid concentration. Depolarization measurements showed that the depolarization ratio (pv) increased with decreasing pH value indicating the increase of anisotropy with increasing acetic acid concentration. Increasing the acetic acid concentration in chitosan aqueous solution caused an increase of the amount of —NH3+ groups on chitosan molecules which led to an increase in intra-molecular electrostatic charge repulsion and chitosan chain expansion. Thus the molecular size, second virial coefficient A2, and depolarization ratio pv of chitosan increased with increasing acetic acid concentration.