Abstract
In this study, hydrogels were synthesized through the radical polymerization of hardwood kraft lignin, N-isopropylacrylamide, and N,N'-methylenebisacrylamide. Statistical analyses were employed to produce lignin-based hydrogels with the highest yield and swelling capacity. The success of the polymerization reactions was confirmed by NMR and Fourier infrared spectroscopy. The lignin-based hydrogel was more thermally and rheological stable, but exhibited less swelling affinity, than synthetic hydrogel. The rheological studies indicated that the swollen hydrogels were predominantly elastic and exhibited a critical solution temperature that was between 34 and 37 °C. Compared with the synthetic hydrogel, lignin-based hydrogel behaved less elastic as temperature increased. In addition to inducing a green hydrogel, the results confirmed that hardwood lignin-based hydrogel would have different properties than synthetic-based hydrogels, which could be beneficial for some applications.