Abstract
In this paper, we report the results of fluorescence probe studies of association in aqueous solution of a model polymer ODU, which is a C18H37 end-capped monodisperse poly(ethylene oxide) with a molecular weight of 35 000 and essentially 100% end group substitution. The main parameter of interest is the end group aggregation number NR, which we determine by the time-resolved fluorescence quenching technique using pyrene as a probe. Aiming to extend this technique to situations where the probe is not solubilized completely by the polymer micelles, which happens when the polymer concentration in a solution becomes very low, we modified the standard Poisson quenching model to account for the emission of the probe in the water phase. ODU solutions undergo phase separation at polymer concentrations between 2.1 g/L and 20 g/L. The aggregation number in a 2.1 g/L solution was found to be 23. For high concentration polymer solutions, from 3 to 17 wt %, we found that the aggregation number tends to increase with ...
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