Polymers bearing recurring amide groups in their backbone are defined as
polyamides. Aliphatic polyamides can be synthesized by condensation of
bifunctional monomers. The two principal commercial polyamides are
poly(hexamethylene adipamide) [nylon 66] and polycaprolactam [nylon 6] widely
used for variety of applications. Reactions of numerous combinations of diacids,
diamines and amino acids have been reported and copolymers having various
proportions of these have been prepared.