EFFECTS OF CROWN ETHERS ON THE INTERFACIAL STRUCTURE OF MICELLES AND VESICLES

Crown-ether (CE) compounds are able to capture the counter-ions near the micellar or vesicular interfaces. The concentration effect of CE addition on the interfacial structure of sodium lauryl sulfate (NaLS) micelles and dihexadecyl phosphate (DHP) vesicles, is studied through two electron transfer reactions: the N,N,N',N'-tetramethylbenzidine (TMB) photoionization and the photocation (TMB+) decay. Previous studies have shown a linear dependence of the photoionization yield vs. the interfacial electrical potential (DELTA-PSI) in negatively charged micelles or vesicles. A relationship between TMB+ dark decay rate and DELTA-PSI has also been demonstrated. In the present study, photoionization yield and TMB+ decay rate display an opposite variation vs. CE concentration. The results are discussed in terms of DELTA-PSI variations.