Structure–property relationships of ring‐containing nylon 66 copolyamides

Several series of nylon 66 copolyamides were prepared with up to 30 mole‐% substitution of ringed comonomers of the type X‐(CH2)n‐R‐(CH2)n‐X, wheren= 0, 1, or 2; X = −NH2or CO2H; and R = phenylene, cyclohexylene, or naphthyle. The ring structure was correlated with glass transition temperature and melting point. The important features of ring structure fall into the following categories: ring isomerism, aromaticity, diamine vs. diacid substitution, chain length, and ring substitution. Proper “fit” (isomorphism) of the comonomer into the nylon 66 chain appears to be the main criterion for ringed copolymers of highTgand high melting point.