Sodium 2-(N-Dodecylamino) naphthalene-6-sulfonate as a Probe of Polymer-Surfactant Interaction. (Reannouncement with New Availability Information)
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Sodium 2-(N-dodecylamino) naphthalene-6-sulfonate (C12NS) was used as an intrinsic fluorescence probe in investigations of the association of poly(N-isopropylacrylamide) (PNIPAAM) with surfactants in aqueous solution. The wavelength of maximum fluorescence emission from C12NS shifts from 430 nm in water to 408 nm in n-butanol; thus the fluorophoremay be used as a reporter of environmental polarity. C12NS concentrations > or = to 20 micron M. The behavior of C12NS is in this respect analogous to that of sodium n-hexadecyl sulfate, which exhibits a Krafft temperature in water of 31 C. Aggregation of C12NS in PNIPAAM solution is accompanied by a blue shift in the emission maximum to 424 nm, a shift similar to that observed when submicromolar concentrations of C12NS are solubilized in sodium n-dodecyl sulfate micelles. Above thelower critical solution temperature (LCST) of PNIPAAM, the polymer-rich phase serves to solubilize even submicromolar C12NS.