Synthesis, Structures, and Properties of Bio-Based Elastomer Poly(Butylene 2,5-Thiophenedicarboxylate-Co-ε-Caprolactone)

A series of poly(butylene 2,5-thiophenedicarboxylate-co-ε-caprolactone) (PBTFCLs) copolymers were synthesized bio-based monomers: 2,5-thiophenedicarboxylic acid (TFDCA), 1,4-butanediol (BDO), and poly(ε-caprolactone) (PCL) diol oligomer. The introduction of flexible caprolactone segments into the PBTF homopolymer backbone was aimed at enhancing and modulating the copolymer's properties. The composition and molecular weight of PBTFCLs were determined using gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR), enabling us to establish the successful incorporation of CL units and their impact on the molecular structure. Thermal and crystallization behaviors were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide-angle x-ray diffraction (WAXD), and small-angle x-ray scattering (SAXS). These analyses revealed that the copolyesters exhibit partial crystallinity and possess good thermal stability. Dynamic mechanical analysis (DMA) and dynamic rheological analysis (DHR) confirmed the compatibility of hard and soft segments within the copolyester backbone, indicating a relatively homogeneous phase morphology. The incorporation of caprolactone segments effectively modulated the copolymer's mechanical properties, imparting a degree of elastic recovery, with crystallinity playing a crucial role in supporting these properties.