FTIR and X‐ray study of polymorphs of nylon 11 and relation to ferroelectricity

Nylon‐11 polymorphs have been studied by x‐ray diffraction and by infrared spectroscopy. A γ or γ‐like phase of Nylon‐11 was produced by treating the metastable δ' phase with gaseous HCl or DCl and then exposing the resulting complex (amidonium salt) to 100% RH H 2 O or D 2 O vapor. An oriented form of the γ or γ‐like phase results from treatment of the oriented δ' phase, but stretching of the unoriented γ or γ‐like phase, obtained by treatment of the unoriented δ' phase, induces a transformation to the α phase stable at room temperature. The use of DCl and D 2 O produced highly deuterated samples with Fermi resonances indicating the relative strengths of the hydrogen bonds are weakest in the α phase, intermediate in the δ' phase and strongest in the γ or γ‐like phase.