Preparation, Structure and Rheological Properties of Konjac Glucomannan-CaCl₂ Electrogel

The gelation property is one of the core functional characteristics of konjac glucomannan (KGM). KGM mainly forms gels through ionic crosslinking, deacetylation and compounding with other colloids. Exploring novel gelation technologies for the precise regulation of KGM gel properties is the research focus in this field. In this work, an alternating current (AC) electric field was applied to trigger KGM gelation in the presence of calcium chloride (CaCl₂). The structure and viscoelastic properties (including storage modulus G', loss modulus G″ and loss factor tanδ) of the gels were analyzed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (RS), scanning electron microscopy (SEM), X-ray diffraction (XRD), simultaneous differential scanning calorimetry/thermo-gravimetric analyzer (DSC/TGA) and rheometer. FTIR and RS revealed that KGM underwent partial degradation and deacetylation under the AC electric field. Calcium ions and chloride ions dissociated from CaCl₂ are adsorbed onto the hydroxyl groups of KGM molecules. KGM molecules constituting the gels still retain partial original acetyl groups. SEM images showed that the gels had a porous structure with a coarse surface. XRD patterns showed the gels contained complex CaCl₂ hydrates. Simultaneous DSC/TGA analysis indicated that the gel with excellent thermal stability exhibited distinct melting endothermic peaks corresponding to CaCl₂ hydrates. Rheological data showed that, apart from KGM concentration, G' and G″ of the gels gradually increased with the elevation of CaCl₂ concentration, applied voltage and electric treatment duration. However, when CaCl₂ concentrations, voltage, and electric treatment time exceeded their respective critical values, both started to decrease. Taking G' as the evaluation index, the optimal preparation conditions for KGM-CaCl₂ electrogel were determined as follows: KGM 0.5%, CaCl₂ 1.2%, electric treatment duration 45 min, and voltage 24 V.