Synthesis and properties of high performance biobased liquid crystal polyester based on furandicarboxylic acid and sebacic acid

In this study, a series of high-performance biobased liquid crystal copolyesters derived from 6-hydroxy-2-naphthoic acid (HNA), 4, 4ʹ-Dihydroxybiphenyl (BP), biobased 2,5-furandicarboxylic acid (FDCA) and sebacic acid (SeA) were successfully designed and prepared via “one-pot” melt polycondensation method. The addition of nonlinear and rigid FDCA units broke the regularity of the molecular chain but increased the chain rigidity, thus, endowing the unique thermal behavior, which the melting temperature decreased from 163.0 to 125.3 ℃, while the glass transition temperature decreased first and then increased slightly to 75.7 ℃ as increased the FDCA units to 7.5 mol%. Furthermore, DSC and XRD results showed that a small amount (1 mol%) of FDCA units did not impair crystallization ability of the copolyesters, whereas excess of FDCA hindered the molecular chain packing. The DMA results also demonstrated that the addition of FDCA restricts the chain motion and improves the rigidity of the copolyester as reflected by the higher storage modulus. The incorporation of nonlinear FDCA units lowered the initial degradation temperature slightly, but still exhibited enough thermal stability to be melt processed as compared with its relative low melting temperatures. The copolyesters exhibited a broad temperature range of nematic liquid crystal phase as well as shear thinning and viscous melt flow behavior, which were beneficial for its melt processing. The tensile strength and modulus of the injection molded splines were in range of 82.51–103.27 MPa and 2.05–2.72 GPa, respectively, which were much higher than the common biobased copolyesters such as PLA, PCL and other FDCA-containing polyesters. The increased modulus and decreased fracture strain of the copolyesters containing FDCA units further verified the high rigidity of the molecular chain. Moreover, the in-vitro cytotoxicity and water contact angle results proved that the copolyesters have good biocompatibility. The resulted copolyesters combined with excellent melt processing ability, mechanical property and good biocompatibility have great promising applications as biomedical and biodegradable materials.