Salt effects on the dilute solution properties of bototo gum (Cochlospermum vitifolium)

Abstract

Salt effects on the dilute solution properties of bototo gum ( Cochlospermum vitifolium ) were investigated. There were measured the intrinsic viscosities of the polymer under study in water, in NaCl (at different concentrations) and in NaCl, CaCl 2 and AlCl 3 , at the same ionic strength (I = 1), using an Ubbelohde viscometer at 25°C. The Huggins intersection model (R 2 ) is more appropriate to determine the intrinsic viscosity than the Kraemer's equation. This parameter tends to reduce with the increase in the salt concentration and the cation charge. The molecules of C. vitifolium gum exudate in water (solvent Φ) tend to adopt a “random coil” conformation, of great volume and radius, which exist in two regimes: diluted and semi-diluted; in the presence of salts, the coils exist only in a diluted regime where they are separate each other. The macromolecules in water have probably an extended ellipsoid shape but in presence of salts, they change to another more compact, probably spherical, with radii and smaller volumes. The knowledge of the behavior of C. vitifolium gum molecules in dilute solutions is an important criterion for its rational use in various industries