Structural analyses of poly(m-xylene-α,α′-diyladipamide) and nylon 66 by 15N solid state NMR

¹⁵N solid state NMR, viz. both ¹⁵N cross polarization (CP) NMR and ¹⁵N CP/magic angle spinning (MAS) NMR, is applied to the structural determination—including molecular orientation—of uniaxially oriented poly(m-xylene-α,α′-diyladipamide) film and nylon 66 fiber on the basis of the chemical shift tensors. In the spectrum of a poly(m-xylene-α,α′-diyladipamide) block sample whose fiber axis was set up parallel to the applied magnetic field, a single main peak with 20% powder pattern (non-crystalline domains) was observed. The small difference in the structure of the main chain between these two uniaxially stretched polyamides was clarified from the chemical shift data of the parallel spectra which reflect the angle between the NH bond and the fiber axis. Determinations of the angles between various molecular-fixed axes and the axis of polymer alignment were tried.