A New Structure of High-Performance Isosorbide-Based Polyester-Polycarbonates and Its Mechanical Behavior

Traditional bisphenol A-based polycarbonate (BPA-PC) has been restricted in food contact materials, particularly those for infants and babies, which has the potential chronic toxicity and estrogenic activity due to the presence of bisphenol A. In this study, a series of high-performance isosorbide (ISB)-based polyester-polycarbonates (PIs-PCLCs) were prepared using ISB, poly(caprolactone) diol, and diphenyl carbonate via melt transesterification polycondensation as a potential alternative to BPA-PC. The properties of the PIs-PCLC samples, such as strength, elongation, and glass transition temperature, gradually varied as increasing the polycaprolactone (PCL)-diol content from 0 to 10 mol %, and a good balance in performance was obtained at around 6.25% of the PCL-diol content. Notably, the PIs-PCLC-6.25 (6.25 represents the molar percentage of PCL diol) sample exhibited a tensile strength of 74.6 MPa, an elongation at break of 83%, a high glass transition temperature (Tg) of 122 °C, and an optical transmittance of 89.2% at 550 nm. This overall combination of properties was comparable to that of certain commercial engineering plastics. The small-angle X-ray scattering results obtained during tensile stretching reveal a transition in the deformation mechanism. While the poly(isosorbide carbonate) homopolymer exhibits craze-dominated fracture characteristics, the PIs-PCLC-6.25 sample demonstrates a shear band-mediated deformation process. This is attributed to the incorporation of flexible PCL diol chain segments, which leads to ductile fracture behavior. In summary, this study presents an efficient and viable strategy for fabricating high-performance PIs-PCLCs, thereby broadening the practical application prospects of high-performance biobased polymeric materials in areas such as food-contact packaging and medical devices.