Viscoelastic behaviour of rapid and slow self-healing hydrogels formed by densely branched arabinoxylans from Plantago ovata seed mucilage

We report rheological characterisation of hydrogels formed by highly substituted brush-like arabinoxylans from Plantago ovata seed mucilage. Two arabinoxlyan fractions with similar molecular weight and linkage compositions are chosen to form gels with distinct rheological properties but a similar network structure. Small and large amplitude oscillatory shear rheology is used to characterise the sol-gel transition as a function of temperature and concentration. Differences in rheology and gelation of the two hydrogels are found to be associated with the different proportion of ‘slow’- and ‘fast’-dissociating junctions stabilised by hydrogen bonds, with the ‘fast’-dissociating junctions playing an important role in rapid self-healing of the gel. Based on the temperature dependence of storage modulus and time–temperature superposition principle in combination with the Arrhenius equation, the activation energies of junction zone dissociation are estimated to be 402–480 kJ/mol and 97–144 kJ/mol for the ‘slow’ and ‘fast’ junction types, respectively.