Insights into the swelling behavior of glucomannan-based eutectogels

Konjac glucomannan (KGM) is a natural hydrogel. This work was aimed to study the swelling and flow behavior of KGM in natural deep eutectic solvents (NADESs). The NADESs were produced by mixing choline chloride/betaine and formic acid/acetic acid at a molar ratio of 1:4. The KGM was stirred in NADESs for 1 hour, and every particular time was observed for free-absorbency capacity and granule size. Additionally, the flow behavior of KGM in varying water contents of NADES and KGM concentrations was observed. The results showed that the equilibrium absorbency capacity and granule size of KGM in NADESs ranged from 1.26 g/g to 2.35 g/g and 75 µm to 80 µm, respectively. The swelling rate of KGM in betaine-based NADESs was higher than that of choline chloride-based NADESs. The lower the pH of NADESs, the lower the swelling rate of KGM. Diffusion rate controlled the swelling kinetics of KGM in NADESs, which fell within the pseudo-Fickian type. NADESs with water content above 60% were required to prepare a strong eutectogel from KGM with a KGM concentration above 2%.