Dynamics of polar solvation in quaternary microemulsions

Steady-state spectroscopy and time-resolved solvation dynamics have been used to investigate the effects the addition of alkanol has on the location of coumarin 343 (C343) in cetyltrimethylammonium bromide (CTAB)/1-pentanol/eyelohexane/water, CTAB/1-heptanol/cyclohexane/water, and sodium dodecyl sulfate/1-heptanol/cyclohexane/water reverse micelles. Steady-state spectroscopy showed that the probe molecule is not sensitive to alkanol chain lengths or water loading. Instead, C343 is sensitive to the surfactant used to form the reverse micelles. Solvation dynamics measurements utilizing ultrafast time-resolved fluorescence-upconversion spectroscopy revealed two solvation reorganization times regardless of the micellar system studied or hydration level. A hundreds of picosecond time component is attributed to collective motion of the interface. Time-zero analysis reveals a substantial relaxation component occurring on the femtosecond time scale.