WATER-SOLUBLE POLYSTYRENE LATEXES AS PHOTOREDOX MEDIA .1. INTERFACIAL FLUORESCENCE QUENCHING AND TRIPLET-STATE ELECTRON-TRANSFER FROM PYRENE AND 1-PYRENEBUTYRIC ACID

Aromatic chromophores (pyrene and 1-pyrenebutyric acid) have been adsorbed on water-soluble polystyrene latex particles (commercially referred to as microspheres) from the aqueous phase. The fluorescence properties and quenching efficiencies of these chromophores have been measured using a zwitterionic viologen SPV (4,4'-bipyridino-1,1'-bis(propanesulfonate)). The quenching mechanism has been found to be diffusion controlled. The electron-transfer quenching of the triplet state by SPV was characterized. Triplet-state quenching does not occur for pyrene embedded in these polystyrene latexes in aqueous solution, which is attributed to the hydrophobic protection of the pyrene from the approach of water-soluble SPV. On the other hand, the efficiencies of charge separation for 1-pyrenebutyric acid both in homogeneous aqueous solution and adsorbed on polystyrene latexes in aqueous solution were found to be high. It is proposed that the amphiphilic 1-pyrenebutyric acid molecules prefer to reside at the aqueous interface of the latexes. These results demonstrate that ''compartmentalization'' of ion pairs, produced by redox quenching, can be achieved when 1-pyrenebutyric acid molecules are located at these interfaces. This provides a strategy for more efficient utilization of excited-state redox processes.