Structure of iodide ion arrays in iodinated nylon 6 and the chain orientation induced by iodine in nylon 6 films

Abstract

Abstract Two species of iodide ions (I 3 − and I 5 − ) are found in iodine—nylon 6 complexes. Orientation of I 5 − arrays (most likely I 2 /I 3 − complex) along the polymer chain and I 3 − ions perpendicular to the chain axis in uniaxially drawn films and in films with planar orientation suggests that there is and intrinsic relation between the direction of iodide ion arrays and nylon 6 chains. When an unoriented film of nylon 6 in the amorphous or the α crystalline form is treated with an aqueous solution of iodine—potassium iodide, the I 3 − species in the resulting iodine—nylon complex lie in planes parallel to the surface of the film, and I 2 /I 3 − units are oriented normal to the surface of the film. The γ form obtained by desorbing the iodine from this complex shows considerable uniaxial rientation with the nylon chains oriented perpendicular to the plane of the film; this orientation is maintained during the γ to α transition. It is proposed that the iodine‐induced orientation of the nylon 6 chains is due to the nucleating effects of the iodide ion species as the iodine diffuses unidirectionally into the film.