Highly Thermally Stable Bio‐Based Polyimides Derived From 2,5‐Thiophenedicarboxylic Acid: Synthesis and Structure–Property Relationships

To address environmental challenges posed by petroleum‐based materials, developing sustainable, high‐performance bio‐based polyimides (PIs) is crucial. Here, a novel diamine monomer, N,N′‐bis(4‐aminophenyl)thiophene‐2,5‐dicarboxamide (TDTPA), was successfully synthesized from renewable 2,5‐thiophenedicarboxylic acid (THDCA). Subsequently, a series of bio‐based TDTPA‐PI films were fabricated via thermal imidization with various aromatic dianhydrides. Comprehensive characterizations revealed that the rigid thiophene ring and amide linkages endowed the films with outstanding thermal stability (Td5% > 430°C, Td10% up to 545°C) and high char yields (51.4%–57.7%). Additionally, the films exhibited robust mechanical properties, including elastic moduli up to 6.73 GPa and tensile strengths up to 158.90 MPa. To elucidate structure–property relationships, gas permeation (CO 2 /N 2 ) was employed to probe molecular chain packing. Separation performance depended significantly on the dianhydride structure; for instance, TDTPA‐6FDA exhibited a CO 2 permeability of 3.01 Barrer, while the dense architecture of TDTPA‐DODDA achieved a competitive CO 2 /N 2 ideal selectivity of 40.21 with a CO 2 permeability of 1.02 Barrer. This work provides a facile synthetic route for thiophene‐based bio‐polyimides, demonstrating their immense potential as sustainable alternatives in high‐temperature applications and green separation technologies.