Deuterium NMR Studies of Water in Oriented Nylon 6 Fibers

Deuterium NMR studies of drawn nylon 6 fibers hydrated with D2O suggest the presence of three types of water and two classes of exchangeable protons. The water exhibits varying degrees of residual orientational order (incompletely averaged quadrupolar interactions) as well as drying characteristics that enable a comparison with interlamellar and interfibrillar water previously defined by small-angle neutron scattering.1 The interfibrillar water is bound the strongest and exhibits the largest (draw-ratio-dependent) quadrupolar splitting in aligned fibers. Dry fibers (whose accessible amide protons have been deuterium exchanged with D2O) show anisotropic powder spectra. The angular dependence of these spectra suggests that two distinct classes of amide deuterons contribute to the spectra, one associated with aligned interfibrillar amorphous chains (with N−D bonds on average normal to the fiber axis) and more isotropic deuterons probably associated with chain folds and variously oriented crystallite surfaces.