Formation of higher cyclic oligomers in polyamide-4,6

An example of morphology-steered chemistry of cyclic oligomers with the example of polyamide-4,6 (PA46) is discussed in this article. The cyclic oligoamide profiles of solid-state post condensed PA46 show an unusual maximum for intermediate cycles consisting of 10 and 12 amide groups, which are formed in the initial stage of solid state post condensation. This is explained from the short chain length at the start of the post condensation, the preorganization of linear oligomers in the lamellar crystal structure, and the occurrence of amide units in the PA46 lamellar folds. Further the development of the cyclic oligomers up to the cyclic hexadecamide is followed on heating the base polymer in the melt at 310 °C, where it showed to react back to the theoretical Jacobsen and Stockmayer distribution.