Polymers of this functional group typically make up the top layer of a thin-film composite membrane. A polymer of this functional group can be synthesized via the Schotten-Bauman reaction by pulling on a film at a water-cyclohexane interface in a namesake “rope trick.” A class of polymers linked by aromatic instances of this functional group includes Nomex. Polymers linked by this functional group can be synthesized via (15[1])ring-opening polymerizations of (*) lactams. Urethanes contain an additional oxygen bonded to the carbon of these functional groups, which appear in Kevlar, nylons, and DMF. One of these functional groups is formed when a carboxyl and amino group condense. For 10 points, name this functional group consisting of a nitrogen bonded to a carbonyl, which links amino acids in proteins. ■END■