Mechanical Performance and Dye Adsorption of Lignin/Poly(ethylene glycol) Diglycidyl Ether/Sorbitol Polyglycidyl Ether Hydrogels

A bisphenol-A-free lignin hydrogel platform with programmable network density is reported. Lignin was crosslinked with poly(ethylene glycol) diglycidyl ether (PEGDGE) and sorbitol polyglycidyl ether (SPE) via epoxide ring-opening to generate hydrogel networks spanning eleven PEGDGE/SPE ratios. A single compositional lever—the SPE fraction—allowed the predictable densification of the network, translating into a monotonic shift in swelling and viscoelastic/mechanical responses. Importantly, the well-performing hydrogel (LS1P9) coupled swelling ratio with adsorption functionality, removing 72% methylene blue from water under the tested conditions. This work positions lignin as more than a passive filler: it serves as an active phenolic macromonomer for designing sustainable, multifunctional hydrogels.