The valorization of lignin resources requires a functionalization path that simultaneously fulfills “green” and scale-up efficiency. In this study, an efficient scalable one-pot method was developed to convert Kraft lignin into esterified lignin derivatives with controlled size, structure and Tg. In particular, the two-step reaction, which was carried out using a “one-pot process”, involved the hydroxyethyl derivatization of phenols and carboxylic acids on lignin with ethylene carbonate, followed by direct esterification using an organic acid. The resulting homogeneous mixtures were fractionated by downward precipitation with water to obtain five different lignin fractions, resulting in a low intensity of the process mass. This one-pot route improved over previous work in which the lignin was recovered after the first modification step. The pot result can esterify about 90% aliphatic hydroxyl groups in the hydroxyethyl derivatives. Analysis with NMR, GPC using multiple detectors and DSC provided a better insight into the structure and properties of technical lignin. 50-60% of the esterified lignin derivatives obtained have a polymeric property with a resulting Tg at about 80 ° C. The remaining 40% -50% of technical lignin are oligomeric with more end group units and a corresponding Tg close to or below room temperature. In solution, these fractions had a conformation that ranged from a rod-shaped structure to dense spheres, indicating a very compact structure for the lignin. As a result, this route has provided a starting material with a nearly complete conformation and is known to provide a detailed understanding of the structural features and properties of lignin-based materials. The integration of ethylene carbonate and organic acid as multifunctional reagents in this way can meet many sustainable chemical needs and provide a clear path to uniform esterified kraft lignin that may be available for various Mt-level applications.