Dynamic viscoelasticity and anomalous thermal behaviour of concentrated agarose gels

Dynamic viscoelasticity measurements, and differential scanning calorimetry (DSC) were carried out, in order to examine the gelling mechanism of concentrated solutions of agarose with two different molecular weights. The dynamic elastic modulus of the gels increases up to about 35°C and then decreases with increasing temperature. The DSC endothermic peak temperature T m accompanying the gel‐sol transition was almost independent of the concentration of the gel, which is quite different from the behaviour of many other thermo‐reversible gels. T m is shifted to higher temperatures with increasing molecular weight of agarose. The endothermic enthalpy was proportional to the concentration of gels for both fractions. A peak characteristic of crystalline material was observed in the X‐ray diffraction pattern of an agarose gel (concentration 15 wt.‐%).