Depolymerized lignin: more defined structure with improved properties

The aromatic-rich nature of lignin combined with its 3D crosslinked structure will provide for unique properties when integrated in polymers, resins or composite materials. However, the high molecular weight and the complex structure of lignin limits its reactivity and compatibility which renders its integration into high-value materials rather difficult. As a way of circumventing this problem, depolymerized lignin fractions gained considerable attention as they will provide for more defined, compatible and reactive lignin structures.

As a first aim of this work, the main differences between technical lignin and depolymerized lignin fractions (oligomers) were evaluated by combining analytical methods with thermal studies. The combination of both techniques allowed us to associate the lignin structure with thermal properties such as the degradation temperature or the glass transition temperature. As a second goal, the chemical modification of the aliphatic and phenolic hydroxyl moieties of the different lignin fractions was examined. 31P-NMR and FT-IR were used to analyze the progress and the yield of the reactions in order to compare the reactivity of technical lignin with lignin oligomers.