Structure–Property Regulation of PA5T /56 Copolyamides and Dual‐Responsive Shape‐Memory Behavior of Their MWCNT ‐ COOH Composites

Semi‐aromatic polyamides (SAPAs) are emerging as promising engineering polymers due to their unique combination of high rigidity, thermal stability, and processability. However, pure SAPAs suffer from limited electrical conductivity and multifunctional responsiveness, hindering their application in smart materials and actuators. In this paper, PA5T/56 copolyamides with varying terephthalic acid/adipic acid molar ratios (3/7–7/3) were synthesized via melt polycondensation and characterized mainly by 1 H NMR, FTIR. PA5T/56 (3/7), with the optimal balance of mechanical performance and processability, was selected as the composite matrix. Composites containing different contents of carboxyl‐functionalized multi‐walled carbon nanotubes (MWCNT‐COOH, 0, 5, 10, 15 wt%) were prepared by solution casting. The effects of MWCNT‐COOH on the thermal stability, mechanical properties, and especially thermo‐ and electro‐induced shape memory behaviors of the composites were comprehensively investigated. The results show that MWCNT‐COOH markedly improves the thermo‐induced shape memory at an appropriate loading, with the shape recovery rate reaching 82.8% and the shape fixity rate exceeding 90% at 10 wt% MWCNT‐COOH. 15 wt% MWCNT‐COOH/PA5T/56 can achieve electro‐induced shape recovery via Joule heating within 44 s. Overall, this work establishes the structure–property relationships of PA5T/56 copolyamide with tailored monomer compositions and demonstrates the effectiveness of MWCNT‐COOH in imparting thermo‐ and electro‐responsive functionalities.