Synthesis and properties of high-performance biobased liquid crystal copolyesters modified by small amount of 2,5-furandicarboxylic acid

High-performance bio-based liquid crystal copolyesters derived from 6-hydroxy-2-naphthalenoic acid (HNA), 4,4'-dihydroxybiphenyl (BP), bio-based 2,5-furandicarboxylic acid (FDCA) and suberic acid (Sa) were successfully designed and prepared by "one-pot" melt polycondensation method. The influence of small amount (1-5 mol%) of FDCA on structure and properties of the copolyesters were fully investigated. Aromatic heterocyclic FDCA units had unique effect on molecular structure and properties of the copolyesters ascribed to its high stiffness and nonlinearity. The glass transition temperature, melting temperature and initial decomposition temperature of the copolyester was improved. In addition, a small amount of FDCA addition was conducive to crystallization, which can be attributed to FDCA addition increasing the molecular chain interaction. The copolyesters exhibited a broad liquid crystal phase temperature range and viscous behavior, which provided great convenience for its melt processing. The tensile strength and modulus of injected splines were in range of 82.38 similar to 121.30 MPa and 2.68 similar to 3.95 GPa, respectively, which were much higher than those of PET, PLA and other biobased polyesters. The obtained copolyester has good thermal stability, melt processing ability, mechanical properties and hydrophilicity, which indicates that they have great potential for medical and packaging applications.