Sodium dodecylsulfate-poly(ethyleneoxide) Interactions studied by time-resolved fluorescence quenching
The interaction between sodium dodecylsulfate (SDS) and poly(ethyleneoxide) (PEO) has been studied by time-resolved fluorescence quenching at 20°C and 40°C in the dilute regime, i.e., 0.2% w/v, and in the semi-dilute regime, i.e., 2% w/v, with respect to PEO. Lifetime measurements show that PEO wraps around the micelle-like cluster formed by SDS upon interaction with PEO — the polymer shields the probe, pyrene, from quenching by bulk water solbuilized oxygen. The aggregation number determined at the SDS-concentration when interadtion starts, CAC, is much lower than predicted by current theory. As the surfactant concentration is increased, the aggregation number is simultaneously increased in the dilute regime, but remains constant at low additions of SDS in the semi-dilute regime. This indicates a certain number of locations for the clusters on the polymer chain. At CAC clusters are formed at these locations. Added surfactant is consumed by forming new clusters until all locations are filled in competition with the growth of excisting clusters.
Key wordsFluorescence quenching sodium dodecylsulfate poly(ehtyleneoxide) interactions aggregation numbers
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