Structure and morphology of odd polyoxamides [nylon 9,2]. A new example of hydrogen-bonding interactions in two different directions

The structure and morphology of nylon 9,2 has been investigated using transmission electron microscopy, selected area electron diffraction, and X-ray diffraction. A unit cell with parameters a = 5.45 Angstrom, b = 8.7 Angstrom, c (chain axis) = 31.8 Angstrom, and beta = 47.9 degrees was determined and a C12/c1 space group is postulated. Chain conformation is practically all-trans, but the torsion angles of the NH-CH2 bonds slightly deviate from 180 degrees in order to optimize the hydrogen-bonding interactions between neighboring chains. A structure with two directions of hydrogen bonding is derived, although the unit cell is strongly related to that found in nylon 6,6. Crystallization from the melt and temperature-induced structural changes have also been studied.