Chemistry and physical properties of sulfamide and its derivatives:proton conducting materials

The state of the art in proton conducting polymers is described and the interest in the use of sulfonamide groups to prepare a series of such polymers is stressed. The most relevant aspects of the chemical and physical characteristics of sulfamide are reviewed. Its history is briefly presented. A detailed description of the structure and molecular environment of crystalline sulfamide is given. Our contribution to the interpretation of the Raman and IR spectra of sulfamide in the 4000–50 cm ^-1 range at melt temperature, 300 and 77 K is reported. The magnitude of the intra- and inter-molecular couplings existent in the NH stretching bands in sulfamide at room temperature and the geometry of the NH ₂ groups in this compound are discussed. The existence of a phase transition is proposed and the participation of hydrogen bonds examined. The protonation and hydrolysis of sulfamide and related compounds are referred to. Reactions with amines, amine exchange and rearrangements of several sulfamide type compounds are analysed. Some data associated with the sublimation of sulfamide are indicated. The effect of ionizing radiation on sulfamide is mentioned. The interpretation of the thermochemistry and pyrolysis of sulfamide suggested in the literature is analysed. Several possible applications of sulfamide in polymer synthesis are pointed out. The results we present indicate that pristine sulfamide may be classified as the fourth known molecule to work as a solvent for acidic protons, in a way similar to water, phosphoric acid or imidazole. Our studies reveal that the electrochemical stability of crystalline sulfamide spans ca. 1 V. Future directions in the field of proton conducting materials based on sulfamide are suggested.