Impact of Lithium halides on rheological properties of aqueous solution of poly(vinyl alcohol)

The present study focused on the effects of the addition of lithium salts such as LiI, LiBr and LiCl on the rheological properties of aqueous solutions containing 15 wt% poly(vinyl alcohol) (PVA). There was a plateau in the shear storage modulus in the low frequency region, demonstrating that such solutions have a network structure attributed to hydrogen bonding of the PVA. The value of the plateau modulus evidently decreased with temperature and with the addition of lithium salts. The experimental results also demonstrated that the anion species in the salt plays an important role in determining the rheological properties, including the magnitude of the plateau modulus. The iodide anion, which is classified as a water-structure-breaker ion in the Hofmeister series, effectively decreased both oscillatory shear moduli including the plateau modulus. However, the effect of adding LiI decreased at high temperatures, owing to the reduced extent of hydrogen bonding.