FLUORESCENCE QUENCHING AND EXCIMER FORMATION TO PROBE THE MICELLIZATION OF A POLY(ETHYLENE OXIDE) POLY(PROPYLENE OXIDE) POLY(ETHYLENE OXIDE) BLOCK COPOLYMER, AS MODULATED BY POTASSIUM FLUORIDE IN AQUEOUS-SOLUTION

The change in aggregation behavior of L-64, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, with the concentration of added potassium fluoride in aqueous solutions has been studied with fluorescence probes and light scattering and viscosity measurements. An important feature is that the L-64 preparation is polydisperse, with some 2% of the material in a more hydrophobic form, probably diblock polymers, which form micellar aggregates at lower temperature and lower salt addition than the bulk of the polymers. This explains nicely the peculiar excimer formation and fluroescence quenching behavior and also a number of other erratic observations previously made.