A novel water-soluble copolyamide based on Nylon 66 was synthesized via solution-melt poly-condensation of hexanedioic acid and sodium 5-sulfoisophthalate with 1,6-diaminohexane. The chemical structures of the products were ascertained by various spectroscopic techniques (FT-IR, Raman, and H-1 NMR). The thermal properties of the polyamides under consideration were measured by TGA and DSC. According to the temperature dependence of FTIR spectra, it was found that the average strength of the intermolecular hydrogen bond of the water-soluble copolyamides becomes weak with increasing the temperature. It was found that the obtained random copolyamides could self-assemble into spherical micelles in aqueous solution with the size dependent on the hydrophilic fraction according to the DLS and TEM measurements. (C) 2013 Elsevier Ltd. All rights reserved.