(501i) Synthesis of Lignin-Based Polyesters

Lignin is an abundant plant-based biopolymer that possesses high concentration of aromaticity which enhances mechanical and thermal properties. The sustainable raw material lignin is produced from a paper industry, where lignin is disposed of as an unwanted byproduct. In addition to its abundance and inexpensive supply, lignin is favorable for its numerous attractive properties, such as biodegradability, antioxidant activity, high carbon content, high thermal stability, and stiffness. These important features of lignin can be synergistically combined with the advanced functionalities of other polymers via covalent bond linkages. This presentation will report poly(lignin-co-poly(ethylene brassylate)) (poly(lignin-co-PEB)). PEB is non-human food vegetable oil, castor oil, based polymer. The poly(lignin-co-PEB) was prepared by two steps: 1) lignin modification to covert hydroxyl group and 2) covalent linking of lignin to PEB. However, there was a serious concern about the linearity of the proposed lignin-based polymers due to lignin’s multiple hydroxyl reaction sites that lead uncontrolled crosslinking. The highly crosslinked polymer does not show thermoplasticity, and therefore is disadvantageous for scalable thermal processing. The talk will discuss solutions of this concern. During the initial lignin modification, the unwanted hydroxyl groups on lignin can be deactivated by capping agents. Then, only very small numbers of hydroxyl group remain in the lignin to avoid unwanted crosslinking. The resulting copolymer, poly(lignin-co-PEB) shows highly controllable thermal properties which is a thermoplastic behavior. In conclusion, the number of carboxylic acids on the modified lignin is precisely controlled to yield a lightly crosslinked (or linear) polymer that is a thermoplastic.