A 12-membered cyclic diamide monomer for nylon 64 was successfully synthesized in fairly high yield (approximate to 45%). The synthesis conditions were varied to see the effect of the diamine and succinyl chloride reactants on yield. Threefold excess of 1,6-hexamethylenediamine (HDA) gave the highest yield, while further increasing the amount of HDA decreased the yield. Using N,N-diisopropylethylamine as acid scavenger resulted in the formation of two different cyclic amides, which were fully analyzed by H-1 and C-13 solution nuclear magnetic resonance spectrometry and mass spectrometry. Copolymerization of cyclic amides with epsilon-caprolactam via an anionic route gave a block copolyamide with a two distinct endotherms in the differential scanning calorimetry analysis. However, copolymerization by the hydrolytic route gave only nylon 6 with terminal 64 units. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 96-103