Biosourced, Performance-Tunable, Monomer-Recyclable Semi-Aromatic Polyamides: Synthesis and Properties

Semi-aromatic polyamides are among the most crucial materials in the field of specialty engineering plastics. However, achieving a balance between their mechanical properties and processability remains a significant challenge. Currently, bio-based semi-aromatic polyamides are mainly synthesized using flexible or polyester-derived monomers. This study introduces an innovative approach by selecting ferulic acid, a degradation product of lignin with a broader natural availability, as the primary raw material. The aromatic backbone of ferulic acid imparts rigidity and heat resistance to the resulting polyamides. A series of ferulic acid-based semi-aromatic polyamides were synthesized via an efficient interfacial polymerization method. The properties of these materials can be tailored by adjusting the structural characteristics of the polymer segments. As the chain length increases, the segmental mobility of the polymer chains is enhanced, leading to a reduction in glass transition temperature from 120°C to 80°C, the thermal decomposition temperature increases from 314°C to 331°C, while the tensile strength decreases from 63.3 ± 3.7 MPa to 58.7 ± 4.7 MPa, lower water absorption, and improved crystallization in response to external stimuli. The development of ferulic acid-based semi-aromatic polyamides in this work offers novel insights into the green advancement of sustainable engineering plastics.