Synthesis of nylon 6,6 copolymers with aromatic polyamide structure

In this article, flexible nylon 6,6 was reinforced with rigid‐chain aromatic polyamides based on poly(4,4′‐diphenylsulfone terephthalamide) (PSA), poly(p‐diphenyl oxide terephthalamide) (POA), poly(p‐diphenylmethane terephthalamide) (PMA), and isophthaloyl chloride (IPC). Various high molecular weight block copolyamides were synthesized by solution polymerization using p‐aminophenylacetic acid (p‐APA) as a coupling agent. Their thermal properties show that the block copolyamides exhibit higher values of T_g and T_m and better thermal stability than those of nylon 6,6, especially the IPC‐modified nylon 6,6. The order of increased thermal properties of copolyamides is IPC > POA > PMA > PSA. From wide‐angle X‐ray diffraction patterns, it was found that nylon 6,6 has two diffraction peaks, that is, 2θ = 20.5° and 23°, while the multiblock copolymers showed only one at 2θ = 20°, indicating a different crystal structure. It was found that the mechanical properties of the IPC‐modified nylon 6,6 were improved more than those of the semirigid copolyamides. The order of tensile strength was IPC > PSA > PMA > POA, but for elongation, it was POA > PMA > PSA > IPC. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2167–2175, 2001