Synthesis and characterization of lignosulfonate-graft-poly (acrylic acid)/hydroxyethyl cellulose semi-interpenetrating hydrogels

Maximizing the use of waste is an important part of the strategy for sustainable development. Lignosulfonate, a waste product with sufficient reactive functional groups, can be used as reinforcing materials in polymer composites. In this work, composite hydrogels composed of lignosulfonate-graft-poly (acrylic acid) AA network and hydroxyethyl cellulose (HEC) polymer chains are synthesized through in situ polymerization and cross-linking reaction. The composite hydrogels have semi-interpenetrating network (semi-IPNs) structure, which is driven by the hydrogen bond interactions between proton-donating PAA and proton-accepting HEC. The mechanical properties of these composite hydrogels, including fracture stress, critical compression and elastic modulus and elongation are investigated by tensile measurements. These composite hydrogels exhibit higher toughness and extensibility compared to conventional PAA polymer hydrogels. Moreover, full recovery of their original shape after the removal of compression stress indicates their excellent shape-recovery property. Due to their porous structure, these hydrogels show stimuli responsive swelling properties in aqueous solution depending on the pH or ionic strength, which facilitate the repeating absorption and removal of dyes. Therefore, this work may open a new pathway to synthesize functional materials based on lignosulfonate.