Molecular Dynamic Simulations Insight Into the Structural Evolution and Mechanical Property of Segmented Polyamide Copolymer Under Deformation

ABSTRACT Understanding and predicting the thermo‐mechanical properties of high‐performance polyamide materials are of great significance to regulate their design, processing, and application. In this work, a series of poly(ether‐ b ‐amide) and poly(ester‐ b ‐amide) copolymers comprised of long chain polyamide (PA 1212) as hard segments and polyether or polyester as soft segments were studied using atomistic molecular dynamic simulations. The glass transition temperature and stress–strain curves of the copolymers were evaluated. The microstructural and morphological evolution, strain‐induced crystallization, and hydrogen bonding response during deformation were also investigated. Two glass transition temperatures attributed to soft and hard segment phases are obtained at about 235 and 363 K, respectively. The tensile strength resulting from strain‐hardening crystallization highly depends on the type and content of the soft segment. The copolymers incorporated with different polyether or polyester content show the opposite evolution of crystallinity thereof. The poly(tetramethylene glycol) and polycaprolactone‐based copolymers exhibit excellent tensile strength resulting from both the crystalline hard segment and soft segment during deformation. The hydrogen bonding density of each copolymer system decreases during deformation and mainly depends on the polyamide segment. This modeling approach reveals the molecular‐level mechanism of strain hardening of polyamide segmented copolymers and guides the design of thermoplastic polyamide elastomers.