Synthesis and characterization of novel nylon 6-b-polyimide-b-nylon 6 copolymers

Abstract

Novel nylon 6-b-polyimide-b-nylon 6 copolymers were synthesized by polycondensation and subsequent anionic ring-opening polymerization methods. Thus, an aromatic amine containing an N-acylated caprolactam moiety, i.e., 4-aminobenzoyl caprolactam (4-ABC), was used as an end-capping agent in the preparation of imide oligomers of 3,3′-dimethyl-4,4′-diaminobiphenyl (Q-tolidine, OTOL), 3,3′4,4′-bi-phenyltetracarboxylic dianhydride (BPDA) and 2,2′-bis(3,4-dicarboxyl-phenyl)hexafluoropropane dianhydride (6FDA). The effects of the rigidity and molecular weight of the oligomers on their solubility in molten caprolactam were determined. The oligomer prepared from a 100/50/50 molar ratio of OTOL, BPDA and 6FDA was found to be the most rigid composition that could be dissolved in molten caprolactam. End-capped oligomers with this composition and different molecular weights were used as difunctional activators for the anionic, ring-opening polymerization of molten 6-caprolactam. The nylon 6-b-polyimide-b-nylon 6 triblock copolymers obtained, which contained 3–7 wt % polyimide, were successfully melt spun into fibers. The incorporation of the nylon 6 segments into the copolymers was substantiated by FTIR spectroscopy, solubility tests and GPC analysis. The fibers of the copolymers displayed mechanical properties superior to those of commercial nylon 6 fibers. The materials also exhibited improved chemical resistance, thermal stability and good melt processibility. © 1995 IUPAC