Effect of carboxylated cellulose nanocrystals on konjac glucomannan/κ-carrageenan composite hydrogels

Konjac glucomannan/κ-carrageenan (KGM/KC) composite hydrogels often fail to meet industrial requirements due to their weak mechanical properties, while nanofillers are potential materials to address this challenge by taking advantage of their nano-size and filling effects. Herein, carboxylated cellulose nanocrystals (C–CNCs) were chosen as nanofillers to regulate the properties of KGM/KC composite hydrogels, with focus on the effect of C–CNCs concentration on the morphological and physicochemical properties. Meanwhile, an in-depth exploration of the possible mechanisms was also underlying. C–CNCs were well dispersed within the KGM/KC composite matrix, which positively enhanced the mechanical strength, as well as increased the apparent viscosity and modulus of the composite hydrogel greatly when the C–CNCs concentration was 10 % (w/w). This is mainly ascribed to the enhancement of hydrogen bond interaction among the KGM, KC, and C–CNCs, which were verified by Fourier transform infrared spectroscopy. Additionally, the results of low-field nuclear magnetic resonance confirmed the presence of C–CNCs in the hydrogel matrix reduced the water mobility of the hydrogel, which improved the freeze-thaw stability of the composite hydrogel. The fitting of the Power law model (R2 > 0.98) showed that the swelling mechanism of KGM/KC composite hydrogels belonged to Fickian diffusion, and the swelling behavior could be regulated by adjusting the C–CNCs concentration. However, the excessive C–CNCs might weakened the interaction of composite hydrogels, which partially explains the reversal of the reinforcement effects seen at the lower additions of C–CNCs inclusion. These results provide a basis for the development and design of KGM/KC-based products with desirable attributes.