LIGHT-INDUCED HYDROGEN EVOLUTION FROM WATER AND THE EMULSION POLYMERIZATION INITIATED BY NEW REDOX SYSTEMS

Hydrogen evolution from water induced by visible light has been investigated. The system contains tris (2,2\u27-bipyridine) ruthenium(II) as the photosensitizer, 1,1\u27-dialkyl 4,4-bipyridinium (viologens) as the electron relay, EDTA as the electron donor, and colloidal platinum as the photocatalyst. The protecting agents of platinum catalyst has dramatic effect on the rate of hydrogen production. The presence of multiphase systems; such as colloidal silica, polyelectrolyte, and micelles, also have a marked effect on the rate of hydrogen generation. This effect was attributed to the enhancement of the quenching efficiency and the retardation of the thermal back reaction of the primary photoproducts.^ The emulsion polymerization of various monomers have been successfully initiated by Ag(I)/sulfite and Cu(II)/thiosulfate systems. Polystyrene latices initiated by both systems were found to be monodisperse and very stable. The surface strong acids initiated by the silver(I)/sulfite system were not hydrolyzable while the surface groups of polymer colloids initiated by the Cu(II)/thiosulfate system would hydrolyze slowly upon prolonged heating. The surface charge density of polystyrene latices initiated by the Cu(II)/thiosulfate system decreased upon treatment with cyanide ions. Utilization IR spectroscopy, the end-groups of polymers initiated by the Cu(II)/thiosulfate system were proposed to be thiosulfuric acids.