Structure and Morphology of Odd Polyoxamides [Nylon 9,2]. A New Example of Hydrogen-Bonding Interactions in Two Different Directions

Abstract

The structure and morphology of nylon 9,2 has been investigated using transmission electron microscopy, selected area electron diffraction, and X-ray diffraction. A unit cell with parameters a = 5.45 Å, b = 8.7 Å, c (chain axis) = 31.8 Å, and β = 47.9° was determined and a C12/c1 space group is postulated. Chain conformation is practically all-trans, but the torsion angles of the NH−CH2 bonds slightly deviate from 180° in order to optimize the hydrogen-bonding interactions between neighboring chains. A structure with two directions of hydrogen bonding is derived, although the unit cell is strongly related to that found in nylon 6,6. Crystallization from the melt and temperature-induced structural changes have also been studied.

Polymorphism of poly(nonamethyleneoxamide) crystal

“…It was reported by Kinoshita [7] that these nylons seems to primarily crystallize into the -form, in which amide groups tilt with respect to the chain axis and form complete hydrogen bonds in the molecular sheets. While, the existence of the crystalline phase similar to the -form have been reported for various aliphatic nylons containing methylene segments with odd numbers, such as nylon-5,6 [8,9], nylon-5,10 [10], nylon-9,2 [11], nylon-6,5 [12], nylon-12,5 [13], and even-odd nylons derived from undecanedioic acid [14]. The wide-angle X-ray diffraction (WAXD) patterns of these nylon crystals give two strong Bragg reflections at d-spacings ca.…”

Reversible changes induced by temperature in the spherulitic birefringence of nylon 6 9

“…More complex geometries have been postulated for the room temperature structures of polyamides containing glycine units [14] and also of several odd-even and even-odd 4 nylons [8,[15][16][17][18][19][20][21][22][23][24][25][26]. These structures were characterized by the establishment of hydrogen bonds along three and two directions as a consequence of the conformational preferences of glycine residues and the inability to establish a saturated intrasheet hydrogen bonding scheme when an all-trans molecular conformation was assumed and odd diamine or diacid units were involved (Figure 1a).…”

Oxalamides as a hydrogen bonding motif in thermoplastic elastomers

“…The most frequent used polymerization method for the preparation of high molecular weight polyoxalamides is the reaction between an oxalate ester and a diamine 105,[109][110][111] .…”

“…Crystalline structures based on Xray and electron diffraction measurements are reported for nylon-6,2, nylon-9,2 and nylon-12,2 109,110,113 . Powder X-ray diffraction patterns have been published for nylon-4,2, nylon-6,2, nylon-8,2, and nylon-10,2 105,111 .…”

“…Up to now only one crystalline structure of a polyoxalamide having an odd number of methylene groups between oxalamide groups, nylon-9,2, has been determined with Xray and electron diffraction 110 . Interestingly, this polymer does not adopt a structure with hydrogen bonds along a single direction, like the α, β and γ forms in conventional nylons.…”