Evaluation of the potential use of biobased syringic acid as a comonomer for fully aromatic copolyesters

Along with 4-acetoxybenzoic acid (4-ABA) and O-acetylvanillic acid (AVA), the syringic acid derivative O-acetylsyringic acid (ASA) can be used as an AB-type comonomer in polycondensation reactions. All three monomers have comparable polycondensation rates, and therefore the copolycondensation of 4-ABA, ASA, and AVA in the melt is expected to yield copolyesters with a random or nearly random macromolecular structure. From a mixture of ASA, 4-ABA, and 4′-acetoxybiphenyl-4-carboxylic acid (4-ABCA), a ternary thermotropic copolyester with a “liquid crystal glass” structure was synthesized. This copolyester has a lower softening temperature and a higher glass transition temperature compared to similar ternary copolyesters based on 4-ABA and 4-ABCA.