Lignin is the second most abundant biopolymer on earth, after cellulose. Like cellulose it is present in all plant cells playing an important role in the structural stability of the cells. Its aromatic nature makes it the largest potential source of renewable aromatic building blocks for polymer industry. The three most common polymeric building blocks are coniferyl (G), coumaryl (H) and synapyl (S) alcohol, which can be linked through various inter-unit linkages. This makes it a rather complex polymer (in contrast to standard polymers like polyethylene glycol (PEG) ) consisting of at least three possible building blocks and at least seven possible linkages. This makes the combinatorics of even small polymers rather daunting. As such, for a given molecular weight, a large number of possible polymer configuration are possible, while the polydispersity of lignin means a sample will consist of a distribution of polymer weights. This stands in stark contrast to materials like diamond, cerium-dioxide or even MIL-47(V), which have a unique atomic topology. As a result, theoretical (quantum mechanical) modeling of lignin has remained in its infancy, while experimental characterization has made it abundantly clear that the composition of “lignin” depends on (1) the botanical source, it even depends on the part of the plant, and (2) the processing and extraction. As a result, there is a huge amount of experimental studies characterizing lignin, since each lignin sample is effectively unique and different. This also makes the use of lignin in applications very challenging due to the variation in starting material.
We therefor aim to shine a light on the atomic structure of lignin polymers and polymer-property relations, going beyond the standard empirical statistical observation of base unit fractions and aliphatic/phenolic hydroxide fractions. By means of exhaustive prototype studies and statistical general sampling a large data base is being constructed of property-structure relations at different levels of theory (going from force-fields to quantum mechanical modelling).
Projects
- DigiLignin [2022-2024, BioEconomy-FWO/EC]
- QuantumLignin [2024-2028, BOF-KP; 1 PhD]