STUDY OF SOLUTION PROPERTIES OF GALACTOMANNAN FROM THE SEEDS OF MIMOSA-SCABRELLA

The rheological properties of the galactomannan from the seeds of a member of the Leguminosae have been studied. The sample used had a mannose/galactose ratio close to 1 and an intrinsic viscosity of 900 ml/g. The viscosity results are characteristic of a random coil polymer with a critical concentration c* = 2.6/[eta] which is similar to the values found for polystyrene and polystyrenesulphonate, but higher than the value obtained for more rigid polysaccharides. The slope of the logarithmic plot of the specific viscosity measured at zero shear rate against c[eta] in the semi-dilute regime was 4.2, a value in agreement with the theoretical predictions for linear polymers interacting by purely topological entanglements. The viscoelastic behaviour was lower than that found for solutions of other galactomannans and this and the less severe dependence of the viscosity on the coil overlap parameter is probably due to lower interactions because of the high galactose content.