Prepolymers, which are accessible from formamides of low molecular weight di- or triamines (formamide-terminated low molecular weight compounds) and di- or polyisocyanates, of the general formula (II): X—[—N(CHO)—CO—NH—R1—NCO]n  (II) wherein X represents a linear or branched aliphatic, cycloaliphatic, heterocyclic and/or aromatic structural unit having 2 to 40 carbon atoms, and which is optionally further substituted and/or optionally comprises one or more heteroatoms, wherein R1 represents an organic radical which may optionally contain one or more heteroatoms and which may further contain one or more additional free isocyanate groups and/or one or more urethane, biuret, carbodiimide, isocyanurate, allophanate, iminooxadiazinedione and/or uretdione structural units, and wherein n≧2; processes for making the same; compositions containing the same; and uses thereof.