Alternating poly(ester amide)s of glycolic acid and ω-amino acids:: Crystalline morphology and main crystallographic data

The unit cell parameters of two alternating poly(ester amide)s constituted by glycolic acid and omega-amino acid units have been determined by interpretation of Xray and electron diffraction patterns. Orthorhombic unit cells containing two chain segments with a nonplanar conformation have been derived. The electron diffraction patterns were rather different from those characteristic of aliphatic polyamides and polyesters with a zig-zag conformation. Chain-folded lamellar crystals have been obtained by isothermal crystallization of dilute diol or glycerine solutions and the crystalline habit has been studied by means of real space electron microscopy. Polyethylene decoration techniques have been applied to evaluate the regularity of the folding surfaces. Diffraction and morphologic data suggest that hydrogen bonds between amide groups were established along a single direction, which coincides with the preferential crystal growth direction. Spherulites prepared from both evaporation of formic acid solutions and melt crystallization have been also studied. Diffraction data indicate that hydrogen bonds are aligned along the spherulite radius. (c) 2007 Wiley Periodicals, Inc.