Synthesis and biodegradation behavior of polyelectrolytes based on poly(vinyl alcohol) and 2-pyrone-4,6-dicarboxylic acid

Abstract 2-Pyrone-4,6-dicarboxylic acid (PDC), a lignin-derived dicarboxylic acid, has been recognized as an attractive biomass-based building block because of its strong acidity and biodegradability. Although various polymers incorporating PDC units into the main chain have been reported, polymers bearing PDC moieties as pendant side groups have not been explored. In this study, we report the synthesis of a novel side-chain-type PDC polymer through selective esterification of only one of the two carboxylic acid groups of PDC with the hydroxyl groups of poly(vinyl alcohol) (PVA). The resulting polymer contained 5–7 mol% PDC units. Notably, even this low degree of incorporation significantly altered the thermal properties and mechanical strength, indicating that the pendant PDC units strongly influence intermolecular interactions and chain packing. Acid‒base titration revealed that the polymer behaves as an effective polyelectrolyte, exhibiting higher acidity than poly(acrylic acid). Biodegradation tests under composting conditions demonstrated degradability comparable to that of pristine PVA. These results highlight a new structural design strategy for incorporating lignin-derived PDC into side-chain architectures and demonstrate its potential as a functional motif for biomass-derived polyelectrolytes.