Aromatic nitrile oxides undergo polymerization by treatment with trimethylamine in dimethyl sulphoxide. Chain lengthehing occurs via the C–O bonds, as shown by the catalytic hydrogenation of such polymers to aroylamides. The apparent degree of polymerization ranges from 15 up to ca. 100 monomer units. These polymers are quite stable in the solid state, but slowly decompose in solution; they do not give the typical reactions of nitrile oxides.