Mesomorphic Form (β) of Nylon 6

Abstract

The structure of poly (e-caprolactam) (nylon 6) in the β mesomorphic form is here examined. The comparison of the diffraction intensity, calculated on modeled structures, with the experimental profiles, collected by us through an automatic diffractometer, is presented. This analysis has put into evidence the following limiting structural features. (a) The β form of nylon 6 is made of small mesomorphic aggregates of chains (where the matter scatters coherently) with axes arranged in a hexagonal lattice (a = b = 0.48 nm; γ = 120°). (b) The chains have disordered conformations (and do not have a definite chirality, as it is the case for the 21 helices in the α and γ forms) with the −CH2− chains close to nearly all-trans (antiperiplanar) and the two dihedral angles adjacent to the amide bond, ±120°) to antiperiplanar (180°). This notwithstanding, the chains are straight and extended. As a result, the mean chain periodicity is close to 0.835 nm. (c) The H-bonds are formed along lines in the [100], [010], and [...