Preparation and characterization of a temperature-sensitive lignin-based Hydrogel

A novel class of hydrogel was prepared by graft copolymerization of acetic acid lignin (AAL) and N-isopropylacrylamide (NIPAAm) in the presence of N,N'-Methylenebisacrylamide (MBAAm) as the crosslinker and H2O2 as the initiator. The impact of AAL content on the hydrogel properties were investigated in terms of their swelling behavior, thermal behavior, and interior morphology. The data showed that these newly synthesized hydrogels were temperature-sensitive. Differential scanning calorimetry (DSC) curves demonstrated that the lower critical solution temperature (LCST) of the lignin-based hydrogels was approximately 31°C. The thermogravimetric analysis (TGA) data revealed that the temperature of rapid decomposition of all the hydrogel samples was within a narrow range of 400 to 410°C. Furthermore, the scanning electron microscopy (SEM) images showed that the pore size of the hydrogel increased with increasing the AAL content.