Rigid Enhancement Strategy to Achieve Carbazole‐Based Polyamide 6 With Boosted Thermal, Mechanical and Anti‐Moisture Properties

ABSTRACT Carbazole‐containing polyamide 6 (PA6) copolymers were prepared by melt copolymerization using a carbazole‐based nylon salt as a rigid comonomer. FTIR and NMR analyses confirmed the successful incorporation of carbazole units into the PA6 backbone. The effects of carbazole incorporation on the multiscale structure, chain dynamics, thermal behavior, mechanical performance, water resistance, and rheological properties of PA6 were systematically investigated. WAXD, DSC, and SAXS results showed that the copolymers retained the typical α‐crystalline form of PA6, while exhibiting expanded lattice spacing, reduced crystal perfection, suppressed crystallization, and enlarged lamellar periodicity with increasing carbazole content. DMA and positron annihilation lifetime spectroscopy further revealed restricted segmental mobility, elevated glass transition temperature, and reduced free volume, indicating a denser amorphous‐phase packing induced by the rigid planar carbazole units. Owing to the combined effects of backbone rigidification and reduced molecular mobility, the copolymers displayed enhanced tensile and flexural properties, improved thermal stability, and significantly decreased water uptake compared with neat PA6. The copolymers also exhibited a markedly increased heat distortion temperature, demonstrating improved thermomechanical stability under load. In addition, the copolymers maintained favorable shear‐thinning behavior together with enhanced low‐frequency melt strength, demonstrating good processability for melt extrusion and film‐forming applications. These results indicate that carbazole‐based copolymerization is an effective strategy for engineering the structure–property relationship of PA6 and for developing high‐performance polyamide materials with improved heat resistance, dimensional stability, and processability.