Luminescence Probe Studies of Ionomers. I. Steady-State Measurements from Nafion Membrane.

Abstract : Steady state luminescence probe methods were used to study the polarity of the ionic cluster phase within Nafion 117 membrane. Three probes, pyrene, a cationic dansyl derivative and Ru(bpy)3(2+) were used. In fully hydrated Nafion membranes (ca. 40% water by weight), these probes report back microenvironment polarities significantly lower than bulk water. In addition, these probes show that the -SO3H sites are chemically heterogeneous. The effects of water content and counterion on cluster phase polarity were also evaluated. The cluster phase can become quite nonpolar when water is removed and/or when a hydrophobic counterion is added. The effects of the Nafion chemical environment on the dynamics and thermodynamics of chemical processes occurring within the polymer are discussed and demonstrated. Originator supplied keywords include: Ion exchange membranes; Luminescence probe studies; Nafion.