Viscoelastic properties of aqueous solutions of amylose–iodine complex at ultrasonic frequencies

Abstract

The viscoelastic properties of aqueous solutions of amylose–iodine at ultrasonic frequencies have been investigated by a torsional method using quartz crystal resonators. The frequency dependences of the storage (G′) and loss (G″) moduli show that the hydrodynamic interaction increases with the addition of iodine. The effects of the intermolecular hydrogen bonds could be observed from the concentration dependence of viscoelastic functions. The concentration dependences of G′ and G″ − ωηs were extremely large, but the concentration dependence decreased with the addition of 2 moles of urea since the effect of hydrogen bonds was minimized. The intramolecular hydrogen bonds seem to affect the hydrogen bonds was minimized. The intermolecular hydrogen bonds seem to affect the tightness of the helical structure of the amylose–iodine complex in water. The frequency dependences of the intrinsic moduli at infinite dilution were compared with the hybrid model theory of Ferry et al. The helical structure of the amylose–iodine complex appears to be more rigid than that of other helical polymers such as poly(γ-benzyl-L-glutamate). However, the flexibility of the helix appears to become more prominent with the addition of urea. When the poor solubility of amylose in water was improved by the addition of ethanol, the conformation of amylose–iodine complex became similar to that in the noncomplex system, where amylose seems to assume a loose and extended helical conformation.