Rheological properties of concentrated solutions of gellan in an ionic liquid

The rheological properties of solutions of gellan were examined at high concentrations where there is entanglement coupling between gellan chains. An ionic liquid 1-butyl-3-methylimidazolium chloride (BmimCl) was used as a solvent. Concentrated solutions of gellan in BmimCl were obtained by using a hot-molding technique. The concentration of gellan was varied from 1.9 x 10(2) to 4.8 x 10(2) kg m(-3). The measurement temperature ranged from 50 to 100 degrees C. The master curve of the angular frequency dispersion of the storage modulus for the gellan solutions showed a rubbery plateau at high angular frequency. The molecular weight between entanglements (M(e)) for gellan was obtained from the plateau modulus. From the concentration dependence curve of M(e), M(e) for gellan in the molten state was determined to be 2.3 x 10(3). (c) 2009 Elsevier Ltd. All rights reserved.