Spherulites from polyamides with a structure characterized by three hydrogen-bond directions

Polyamides constituted by glycine residues have a peculiar structure characterized by the establishment of intermolecular hydrogen bonds along three different directions. Spherulites of polyglycine and nylons 2/3, 2/3/3, 2/6, and 2/11 have been obtained from evaporation of concentrated solutions or from the molten state. In all cases, a negative birefringence was detected. This fact differs from the observations on spherulites of conventional nylons where intermolecular hydrogen bonds are formed along a single direction and sheet structures are postulated. Polarizing light, scanning electron, and transmission electron microscopy showed that banded spherulites are usually formed in the crystallization of nylons 2/n. (C) 2002 Wiley Periodicals, Inc.