Synthesis, physical properties and enzymatic degradation of bio-based poly(butylene adipate-co-butylene furandicarboxylate) copolyesters

A series of bio-based poly(butylene adipate-co-butylene furandicarboxylate) (PBAFs) copolyesters were synthesized from 2,5-furandicarboxylic acid (FDCA), adipic acid (AA), and 1,4-butanediol (BDO) through a two-step polycondensation reaction. The copolyesters were characterized by 1H NMR, GPC, DSC, XRD and tensile tests, and their enzymatic degradation behaviors were also investigated. They were random copolymers whose composition was well controlled and the weight average molecular weight (Mw) ranged from 54,100 to 76,800 g/mol. By combining the results of DSC and XRD, with increasing FDCA content, PBAFs changed from semi-crystalline polymers to nearly amorphous polymers, then to semi-crystalline polymers again. Specifically, the crystallizability and melting temperature (Tm) decreased with FDCA content 0-50 mol%, but rose again at FDCA content 75-100 mol%. And, the glass transition temperature (Tg) increased continuously with increasing FDCA content. Consequently, the tensile modulus and strength decreased but the ultimate elongation increased at lower FDCA content (0-50 mol%), which were converse at higher FDCA content (75-100 mol%). Especially, the P(BA-40 mol% BF) shows outstanding elasticity and rebound resilience. In addition, the influences of FDCA content on the enzymatic degradation by lipase from porcine pancreas were studied in terms of the weight loss and morphological change. At FDCA content of 0-50 mol%, the copolyesters showed biodegradability but only the degradation rate of P(BA-10 mol% BF) was faster than PBA. When the FDCA content were 75-100 mol%, they were actually un-degradable. Thus, depending on their composition, PBAFs might find applications from biodegradable elastomers to thermoplastics.