The role of polymer flexibility on the interaction with surfactant micelles: poly(vinyl alcohol) and sodium dodecyl sulphate aqueous micelle interactions studied by dynamic fluorescence quenching

The interactions between poly(vinyl alcohol) and the surfactant sodium dodecyl sulphate in aqueous solutions have been investigated by means of static and dynamic fluorescence measurements. By static fluorescence measurements the onset of interaction, the critical aggregation concentration, is determined to be 6.5 mM at 20 °C and 7.0 mM at 40 °C. By dynamic fluorescence measurements without added quencher the influence on the lifetime of the fluorescent probe, pyrene, by the presence of the polymer is investigated. From measurements with an added quencher, dimethylbenzophenone, the surfactant aggregation numbers of the micellar aggregates formed upon interaction between the surfactant and the polymer and the quenching rate constant are obtained. At the two polymer concentrations, i.e., 0.2% and 2.0%, the surfactant aggregation numbers at low surfactant concentration are very small, but increase rapidly with increasing surfactant concentration. Comparisons are made with results from a system where poly(ethylene oxide) instead of poly(vinyl alcohol) is the polymer. Key words: dynamic fluorescence quenching, polymer–surfactant interactions, aggregation numbers.