A series of copolyamides of various compositions of nylon 6 and nylon 6,18 were produced. Increased resistance to organic solvents resulted from greater incorporation of nylon 6,18, as shown by decreasing solubility. High-resolution solution NMR indicated there were four amide carbonyls that corresponded to the four possible pairs of comonomer units, allowing detailed composition determination. The melting points of the comonomers decreased as the ratio of hydrogen bonding amide units to methylene groups increased, going from nylon 6 to copolymers with an increasing number of nylon 6,18 repeat units.