Biodegradable Elastomer from 2,5-Furandicarboxylic Acid and ε-Caprolactone: Effect of Crystallization on Elasticity

Most biodegradable thermoplastic materials cannot be used as elastomers due to their relatively poor elasticity. Poly(butylene furandicarboxylate-co-epsilon-caprolactone) (PBFCL) copolyesters were synthesized from 2,5-furandicarboxylic acid (FDCA), 1,4-butanediol, and poly(epsilon-caprolactone) diols. The PBFCLs are susceptible to hydrolysis and enzyme degradation, and the degradation rate could be controlled by the enzymes. PBFCL40 and PBFCL50 (CL molar content) displayed high tensile strength (>= 50 MPa), good elongation at break (>= 1050%), and quick shape recovery like an elastomer. Although BF and CL segments were incompatible, the dynamic mechanical and rheological results excluded the possibility of microphase separation under room temperature. In situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) measurements revealed the evolution of crystals during stretching. Strain-induced orientation, melting of original crystals, and formation of fibrillar crystal occurred in different strain regions, and the surviving crystals acted as the physical cross-linking points. This viewpoint was further confirmed by measuring the recoverability during cyclic tensile tests in PBFCL40 and PBFCL50 with controlled crystallinity. With controlled crystallinity, samples gained adjustable elasticity.