PA6 ‐b‐ PSU ‐b‐ PA6 Triblock Copolymers With Synergistically Enhanced Thermal, Mechanical, and Moisture Resistance Properties

Polyamide 6 (PA6) has attracted extensive attention as an engineering thermoplastic because of its balanced mechanical performance and excellent processability. Nevertheless, its susceptibility to moisture and insufficient thermal dimensional stability remain major obstacles to its application under harsh service conditions. In this study, a triblock copolymer design was employed to address these issues by integrating rigid aromatic polysulfone segments into the PA6 molecular chain. Carboxyl‐terminated polysulfone (C‐PSU‐C, M n ≈5000) was first synthesized via an end‐functionalization strategy and subsequently used as a macromolecular comonomer during the hydrolytic polymerization of ε‐caprolactam, leading to the formation of PA6‐b‐PSU‐b‐PA6 block copolymers. Owing to the covalently connected block structure, the incompatibility between PA6 and PSU was effectively alleviated, resulting in improved interfacial homogeneity and enhanced thermal stability with decomposition temperatures above 370°C. The incorporation of rigid PSU segments simultaneously improved the stiffness, strength, heat resistance, and moisture resistance of copolymers. In particular, the sample containing 20 wt% C‐PSU‐C exhibited a markedly reduced 96 h water absorption of 2.02%, together with a substantial increase in HDT from 57.8°C to 86.7°C. The tensile and flexural strengths reached 80.3 and 114.3 MPa, respectively, which were significantly higher than those of pure PA6.