This paper concerns the influence of the chemical structure on the physical properties of some polysaccharides. Especially, we proposed to discuss the role of the substituents on these properties. In some cases, non-carbohydrate substituents play a minor role on rheological properties in the presence of a salt excess as shown on xanthan and succinoglycan. The rheology of aqueous solution of these stereoregular polysaccharides is controlled by the conformation (helical conformation) whose stability is not largely influenced by these substituents. On the other hand, the interaction between galactomannan and xanthan depends on the presence of acetyl substituents on xanthan but also on the xanthan conformation. However, for polymers such as gellan, XM-6 or BEC 1615, complete deacetylation induces the ability to form physical gels in given thermodynamic conditions. The presence of carbohydrate substituents or short side chains was also examined. Especially in the gellan family, the role of position of substitution (position 3 on the glucose unit C or position 6 on the A glucose) was presented. It is concluded that the substituents giving the higher stability for the helical conformation (higher DeltaH and Tm values) also cause a lower salt sensitivity for the helical stability. The role of the substituents on the properties is also described for natural polymers and their chemically or enzymatically modified derivatives.
