Fractionation of Industrial Softwood Kraft Lignin: Solvent Selection as a Tool for Tailored Material Properties

A simple approach for the fractionation of industrial softwood kraft lignin is presented in this work aimed at predictively obtaining readily usable lignin fractions with tailored material properties in a straightforward manner. This method is based on the use of three distinct solvents of different chemical nature to isolate soluble and insoluble fractions from the parent lignin by a single-step extraction process. A thorough characterization of the soluble and insoluble lignin fractions highlighted a direct correlation between the chemical-physical characteristics of the extraction solvent and the final properties of the recovered materials. In particular, hydrogen bonding interactions between solvent and lignin were demonstrated to play a major role in the extraction process, controlling to a great extent the final materials properties. The results of this study give a clear demonstration of a straightforward approach to access easily lignin fractions with well-defined characteristics and provide strong evidence of the direct correlation between solvent characteristics and properties of the extracted materials as predictive tool for the development of high-performance lignin-based systems. (Figure Presented)