Effect of urea on the conformation and chain flexibility of chitosan molecules with various degree of deacetylation

Abstract

Chitosans with various degrees of deacetylation (DD) were prepared from red shrimp (Solenocera prominentis). DD of chitosan was determined by infrared spectrum. The effect of urea on the conformation and chain flexibility of chitosan molecules with various DD was studied. The results show: 1) The intrinsic viscosities of chitosan solutions containing 4 M urea were higher than those without urea addition. It indicated the chitosan molecules in solutions containing urea have higher hydrodynamic volume than that without urea. It may due to urea increasing the intramolecular hydrogen bond formation. 2) The persistence lengths of chitosan molecules were longer in solutions containing 4 M urea than that without urea addition. The results indicated the molecules were more extend in solutions containing urea than that without urea. 3) Addition of 4 M urea to chitosan solutions rendered the Smidsrod chain stiffness parameters lower than that without urea addition. It indicated that the possible attribute of degree of polymerization on the persistence length may be rule out.