Synthesis of Odd–Odd Bio-Based Polyamide 5,9 as a Path to Practical High-Performance Green Materials

This study explores the properties of polyamide 5,9 (PA-5,9), a fully bio-derived alternative to conventional petroleum-based polyamides such as polyamide 6,6 (PA-6,6) and polyamide 6,10 (PA-6,10). The polyamide is synthesized using pentamethylene diamine (PMDA), derived from the decarboxylation of lysine, and azelaic acid, sourced from vegetable oils, offering a sustainable route to high-performance materials. PA-5,9 exhibits mechanical properties that are competitive with, and in some cases superior to, traditional polyamides, with an ultimate tensile strength (UTS) of 48 MPa and elongation at break of 217%. Thermal stability, water uptake, and gas transport characteristics are similar, and a lower melting temperature facilitates processing. Like other bio-based industrial polyamides such as polyamide 11 (PA-11) and polyamide 4,10 (PA-4,10), this bio-derived polyamide offers a reduced carbon footprint due to its lower processing temperature and competitive cost of raw materials, positioning it as a valuable material in industries seeking sustainable materials. Further analysis demonstrates the pseudohexagonal odd–odd chain structure of PA-5,9 does not compromise its hydrogen bonding ability, maintaining crystallinity levels comparable to standard industrial resins. These results indicate PA-5,9 is well-suited for automotive, textiles, and electronics applications, presenting a promising future for bio-based plastics.