Abstract
Various homo- and copolyureas were prepared either by conversion of diamines with diisocyanates or by heating diamines with N, N'-bisphenoxycarbonyl diamines. The 13C-NMR spectra and the natural abundance 15N-NMR spectra were measured in trifluoroacetic acid. In contrast to polyamides, the carbonyl signals of polyureas are not sensitive to neighboring residue effects, so that 13C-NMR spectra are in most cases useless for the sequence analysis of copolyureas. The 15 N-NMR signals of urea groups are, however, sensitive to the influence of both substituents and thus contain information on the sequence. Structure/ shift-relationships are discussed, and 15 N-NMR spectra of various copolyureas are presented.