FLUORESCENCE AS A PROBE FOR EXAMINING SALT GROUP ASSOCIATION OF SULFONATED POLYSTYRENE IONOMERS IN TETRAHYDROFURAN

Salt group association in sulfonated polystyrene ionomers with different counterions ((SP)Me) was studied over a wide range of concentrations in tetrahydrofuran (THF) by a fluorescence molecular probe technique. It was found that the tendency to form intra-chain associations in the dilute solution regime decreases in the order (SP)Zn > (SP)Na > SPS, where (SP)Zn is the zinc salt, (SP)Na is the sodium salt, and SPS is the sulfonic acid form of the ionomer. The critical concentration, when inter-chain associations become important, decreases in the order polystyrene approximately SPS approximately (SP)Na >> (SP)Zn. Some speculations about the structure of the salt group associations are presented on the basis of the monomer-excimer fluorescence data from (SP)Me solutions.