Bio-based polyamides with designer crystallinity from oxidative upgrading of tung oil

Transforming non-edible plant oils into high-performance engineering polymers offers a promising route toward sustainable materials, yet remains challenged by the inefficient upgrading of structurally complex feedstocks and the difficulty of simultaneously controlling crystallinity, toughness, and processability in the resulting polymers. Tung oil, a renewable resource rich in conjugated polyunsaturated fatty acids, is particularly attractive but has been underutilized because selective conversion into well-defined monomers remains difficult. Here we report an integrated strategy that links feedstock upgrading with molecular structure programming to create bio-based polyamides with designer crystallinity. Through hydrogen peroxide-assisted oxidative cleavage, tung oil is selectively converted into high-purity azelaic acid (AA), which is subsequently copolymerized with hexamethylenediamine and poly(propylene glycol) bis(2-aminopropyl ether) (D400) to construct a family of random copolyamides (PA69 X ). The incorporation of flexible ether-containing segments disrupts chain regularity and hydrogen-bond organization, enabling precise modulation of crystalline order, melting behavior, and lamellar structure while preserving excellent thermal stability. As a result, the materials undergo a transition from rigid semicrystalline polyamides to highly tough elastomers with programmable crystallinity. The optimized copolyamide exhibits a fracture toughness of 141 MJ m −3 together with continuous melt-fiber processability, stretch-induced crystallization behavior, and robust reprocessable adhesion to metal substrates with lap shear strengths exceeding 9 MPa. This work establishes a general framework that integrates renewable feedstock valorization, crystallinity engineering, and multifunctional performance, providing a pathway for converting underutilized plant oils into sustainable engineering polymers.