Thermal Treatment of Semi-dilute Aqueous Xanthan Solutions Yields Weak Gels with Properties Resembling Hyaluronic Acid

Semi-dilute (ca 2 g/dl) aqueous xanthan (mean molar mass ca 1 x 10(6) g/mol), when heated in the presence of 0.1 M NaCl to a temperature above the order<-->disorder transition temperature, forms highly viscoelastic solutions when returned to room temperature. The steady shear and dynamic rheological behaviour of these solutions discloses a weak gel structure, the viscosity of which is unusually sensitive to the rate of shear. In shear thinning behaviour these heat and salt treated xanthan solutions mimic the properties of the aqueous hyaluronic acid solutions widely used in viscosurgical techniques. The double stranded model of native xanthan is invoked to interpret the observed behaviour of heat and salt treated semi-dilute aqueous xanthan.