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.
Keywords: Arabinoxylan; Hydrogen bonding; LAOS; Mucilage; Plantago ovata; Rheology; SAOS; Self-healing gels.
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