Measurement of the intersheet shear along the chain axis in nylon 6

X-ray and electron diffraction studies on solution-grown crystals of high-f idelity, monodisperse;nylon 6 oligoamides have provided the opportunity to measure, by experiment, the intersheet chain-axis, or c-axis shear (Deltac) . For almost 50 years this Deltac value for the classical alpha -structure of nylon 6 has been taken, by analogy with nylon 6 6, to be 0.37 nm. Our ev idence suggests that the ac value is likely to be 0.14 nm and certainly low er than 0.21 nm. In addition to crystallizing the 5-amide nylon 6 oligomer in the alternating intersheet sheared a-structure, we have crystallized thi s monodiperse oligomer in the progressively intersheet-sheared lambda -stru cture. In this structure we find that Deltac = 0.35 nm, a value we have als o independently discovered for the lambda -structure of nylon 8. Modeling t he intersheet interaction energy, as a function of incrementally changing D eltac, gives two Deltac values: 0.14 and 0.36 nm. These values closely matc h our experimental results.