RHEOLOGY OF HYDROXYETHYLATED STARCH AQUEOUS SYSTEMS - ANALYSIS OF GELFORMATION

This paper reports dynamic viscoelastic and steady shear measurements of aqueous solutions of two commercial hydroxyethyl ethers of potato s tarch, allowing us to define three different viscoelastic regions, dep ending on the polymer concentrations. The fluid-like zone (I) correspo nds to a homogeneous solution, free of associations between chains, wh ere the linear viscoelastic model can be applied; the fluid-gel transi tion zone (II) is associated with the theology of complex systems whic h possess intermolecular specific interactions; and the gel-like zone (III) involves a network formation giving rise to a gel. The reversibi lity of the hydrogels was studied by means of steady/dynamic transient experiments allowing breakdown of the gel network and analysis of reh ealing. Comparing the elastic moduli of the starch derivative gels lea ds us to assume that the functionality depends on the capacity to form hydrogen-bonding associations between polymer chains.