Morphology and local chain structure of polyamide 6 modified in the solid state with a semi-aromatic nylon salt

Structural and conformational differences between the polyamide 6 (PA6) homopolymer and two copolymers of PA6 modified in the solid state with 20 and 30 wt% of the semi-aromatic nylon salt of 1,5-diamino-2-methylpentane (Dytek A) and isophthalic acid (IPA) in the feed were investigated. Room temperature wide-angle X-ray diffraction (WAXD) analysis together with 13C{1H} cross-polarization/magic-angle spinning solid-state (CP/MAS) NMR and 2D 13C{1H} FSLG-HETCOR experiments showed that there is no co-crystallization of the Dytek A-isophthalic acid (DyI) salt with the PA6 repeat units. A steady decrease of the degrees of crystallinity with increasing amount of the incorporated DyI salt was proven. Upon heating of the samples a transformation of trans conformers into gauche conformers of the polymer chain fragments was observed both by performing temperature-dependent FT-IR and solid-state NMR experiments.