Structure and Morphology of Thermoplastic Polyamide Elastomer Based on Long-Chain Polyamide 1212 and Renewable Poly(trimethylene glycol)

Novel biobased thermoplastic polyamide elastomers (TPAEs) were synthesized using a long-chain polyamide 1212 (PA1212) oligomer and 100% renewably resourced poly(trimethylene glycol) (PPDO) via a facile "two-step"melt polycondensation. The TPAEs are lightweight, with a density of 1.04∼1.05 g cm-3. The structure and morphology of the TPAEs with high biocontent were investigated by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), atomic force microscopy (AFM), transmission electron microscopy (TEM), and dynamic thermomechanical analysis (DMA). The results show that the new biobased TPAEs have a clearly microphase-separated structure comprising quite low crystalline PA1212 segments and an amorphous PPDO segment at room temperature. The spherical rigid PA1212 domains for PA624-PPDO with a diameter of about 100 nm can well disperse in the amorphous PPDO phase. Moreover, the rigid PA1212 segments mutually interconnect with the increasing molecular weight of the PA1212 oligomer, and the typical PA1212 spherulites about 200 nm with lamellae structures have been found in PA2200-PPDO, filled with amorphous PPDO in the interlayer. Since the structure and morphology characteristics, the storage modulus (E′) of TPAEs quickly decreases from about 3000 MPa in a glassy state to 400 MPa in a rubbery state. Furthermore, long-chain PA1212 segments contribute to the outstanding thermal stability; i.e., the initial decomposition temperatures of all TPAEs are over 360 °C. The novel biobased TPAEs with good low-temperature elastic, high elastic recovery, and good thermally stable properties are expected to have potential applications in CO2 separation and breathable dressing.