Synthesis and Characterization of Biobased Polyesters Containing Anthraquinones Derived from Gallic Acid

To study the effects of the main and side chains on the physical properties of polyesters containing anthraquinone substituents, two types of 1,5-dihydroxy-2,3,6,7-tetraalkoxyanthraquinones (DHTAAQs) were prepared from gallic acid, a major component of hydrolyzable tannins, and polymerized with five dicarboxylic dichlorides by interfacial polymerization. The solubility of the fabricated polyesters was strongly affected by the alkoxy side chains of the DHTAAQ units. Conversely, their thermal decomposition behavior depended on the structure of the dicarboxylate units. The thermal properties of the anthraquinone-based polyesters were influenced by both the dicarboxylate units and alkoxy groups, and their glass transition temperature could be controlled over a wide range (81–308 °C). To design DHTAAQ-based polyesters with adequate solubility and high heat resistance, it is preferable that first suitable alkoxy groups are selected to provide the necessary solubility, and then appropriate aromatic dicarboxylate units are chosen to obtain the required thermal properties.