The aggregation of alkyltrimethylammonium surfactants Ci2TA+ and CieTA+ in dilute water solutions of sodium poly(styrenesulfonate) has been investigated. Aggregation numbers were estimated with the time-resolved fluorescence quenching technique. In the calculations, results from binding isotherms and solubility measurements were used. Binding isotherms for dodecyltrimethylammonium bromide to the polyelectrolyte were determined using a surfactant-selective electrode. The aggregation numbers were found to be independent of the concentration of surfactant and type of counterion, but to increase with increasing surfactant tail length. From the kinetics of the quenching of pyrene fluorescence with hydrophobic and hydrophilic quenchers, it was concluded that compact aggregates with net negative charge were formed, in which the polyelectrolyte is intimately associated with the surfactant. The aggregates are joined by surfactant-free parts of the polyelectrolyte chain, the lengths of which depend on the amount of bound surfactant. The quencher dimethylbenzophenone was found to migrate between the aggregates at the highest concentration of the long-tailed surfactant.

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The dynamics of unimer exchange between aqueous micelles, formed by two amphiphilic block copolymers, i.e., poly(styrene-b-sodium methacrylate) and poly(tert-butylstyrene-b-sodium methacrylate), has been investigated by steady-state fluorescence spectroscopy. The kinetics are so slow at room temperature that no exchange could be detected over several hours, while at 60 °C the exchange rate constants could be estimated. These results corroborate our previous findings that the rate is slowed down by increasing the hydrophobicity of the core. In addition to the temperature, the exchange can also be tuned by the addition of either a cosolvent or a cosurfactant. The efficiency of these additives to speed up the exchange process is related to their water solubility and their compatibility with the hydrophobic core of the micelles. The most pronounced effect on the exchange process is observed when the water solubility is low and the mixing of the additive with the hydrophobic core is favorable.