Electron microscope‐electron diffraction investigations of the crystalline texture of polyamides

Abstract

Abstract Continuous films and discontinuous aggregates of nylons were prepared and examined with combined electron diffraction and electron microscope techniques. It was found that the electrons destroy the diffracting ability of the crystals without affecting their shape. The consequences of this fact for the electron microscopy of polymers are pointed out. It was found that the molecules and the planes containing the hydrogen bonds tend to lie in the film plane, but deviations from this orientation amounting to a maximum of 25° were also found. An expression is derived for establishing the fiber axis direction from single, tilted electron‐diffraction patterns. In some films, a spherulitic morphology was observed which consists of a flat layer structure within the film plane. In general, however, the spherulites develop through a fibrous texture, which appears to arise through the curling up of flat sheets. These sheets themselves possess a fibrous morphology. The spherulitic orientation, as established previously by x‐rays, could now be identified within submicroscopic fibrous aggregates. By examination of individual sheaves in the selected area we could identify ribbons and fibrils which can be considered as being the equivalents of single crystals. The molecules were found to be lying at large angles to the length of even the smallest fibrils. The conclusion was reached that this requires a regular, sharply folded configuration of the molecules, which would also account for the uniform width of the microfibrils. The implications of this new concept are discussed, and earlier models are reviewed in the light of the new facts.