Synthesis, Structure, and Dispersion Property of a Novel Lignin-Based Polyoxyethylene Ether from Kraft Lignin and Poly(ethylene glycol)

In this study, a novel and water-soluble lignin-based polyoxyethylene ether (KL-PEG) was synthesized from kraft lignin (KL) and poly(ethylene glycol) (PEG). PEGs with various polyoxyethylene ether lengths were functionalized preferentially with epichlorohydrin using BF3-Et2O as the Lewis acid catalyst and then grafted onto KL by blocking the phenolic hydroxyl groups. The generated KL-PEG copolymer was purified successively by extraction, dissolution, and precipitation using butanone, alcohol, and diethyl ether, respectively. The effect of reactant ratios on the structure of the KL-PEG copolymer was investigated by Fourier transform infrared spectra (FTIR), ultraviolet spectrophotometer (UV), gel permeation chromatography (GPC), and functional groups content determination. Solubility and FTIR results revealed the successful introduction of PEG into KL. The PEG content in the KL-PEG copolymer could be controlled by varying the mass ratio of PEG to KL, and the molecular weight could be governed by the molar ratio of epichlorohydrin to PEG. The KL-PEG copolymer was further used as a novel dispersant for 50% dimethomorph suspension concentrates and showed better dispersing and rheological properties comparing with lignosulfonate and PEG. This novel amphiphilic KL-PEG copolymer possessing a renewable lignin backbone and branched PEGs could be a promising dispersant for similar applications, including agricultural suspension concentrates.