Synthesis, structure and crystal morphology of nylon 16

The new polyamide nylon 16 was produced by polycondensation of 16-aminohexa decanoic acid in bulk at 210 degrees C. The monomer was obtained by ring-op ening hydrolysis of 2-azacycloheptadecanone which was prepared from commerc ial 8-cyclohexadecen-1-one through a four-step synthesis route. The poly me r has a molecular weight of 13 000 and melts at 164 degrees C. Fiber X-ray diffraction and single crystal electron diffraction measurements revealed t hat nylon 16 crystallizes in a monoclinic lattice with the parameters a = 0 .483 nm, b = 0.935 nm, c = 4.16 nm (chain axis), gamma = 121 degrees contai ning two chains in the unit cell. The packing for the chains was found to b e similar to that described for the gamma-form characteristic of nylons, wh ereas a crystal phase in the alpha-form was not observed. Lamellar crystals of nylon 16 grown in 2-octanol were examined by electron microscopy, and t heir structure and morphology is discussed in relation to the crystal model conventionally accepted for the gamma-form of nylons.