Structure and thermal stability of aliphatic polyoxamides

Abstract

SynopsisA homologous series of aliphatic polyoxamides, nylon 122, 102, 82, and 62, were p r e pared by the bulk polycondensation of dialkyl oxalates with diamines. Infrared spectroscopy, x-ray diff raotion, differential thermal analysis, thermogravimetric analysis, and gas chromatography were used to study the structure and thermal stability of these polxoxamides. From the fiber pattern of nylon 122, a structural repeat distance of 19.5 A was measured. This was in close agreement with the expected value for an extended planar, zigzag chain conformation. With the exception of the expected decrease in the structural repeat distance along the chain axis resulting from the different number of methylene groups, nylons 122,102, and 82 were isostructural. Nylon 62 appeared to pack in a similar manner to the other materials studied. However, there were differences in the diffraction pattern of this polymer; these may be indicative of a different chain conformation or of strain in the crystalline regions of the polymer. The infrared spectra indicate the presence of strong hydrogen bonding in all the polymers. Thermal analysis and pyrolysis data revealed catastrophic polymer degradation between 400 and 500°C in nitrogen, with appreciable homolytic cleavage of the oxamide group.

Oxalamides as a hydrogen bonding motif in thermoplastic elastomers

“…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 . For all even nylon-X,2 polymers, an extended planar zig-zag conformation was proposed with intermolecular hydrogen bonding between neighboring chains in a single direction.…”

“…Since then, several patents and technical papers pointed out that oxalamide based polyamides possessed some interesting properties like unusual solubility characteristics, unusual high moduli of shaped materials, high melting temperatures and low water absorption 105 .…”

“…Polyoxalamides cannot be easily prepared by regular polymerization techniques as used in the synthesis of polyamides since the melting temperatures are mostly close to their thermal decomposition temperatures [105][106][107] . Melt polycondensation of oxalic acid with diamines is accompanied by thermal degradation of oxalic acid as well as the polymer.…”

“…Thermal degradation studies using thermal gravimetric analysis (TGA) revealed that degradation of polyoxalamides starts at temperatures lower then 300 (Figure 2.9b) 105,107,117 . Decomposition occurs between 400 and 475 by homolytic thermal cleavage of the oxalamide group.…”

“…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] .…”