Characterization of fluorescent surfactant aggregates by fluorimetric and viscosimetric techniques

摘要

A combination of fluorimetric and viscosimetric methods was used to characterize N,N-dimethyl-N-2-(4-(t-butylphenoxy)ethoxy)ethyl-N-hexadecylammonium chloride (BDHC), a double-tailed surfactant with dissimilar tail groups. BDHC was observed to fluoresce at 315 nm when excited at 274 nm, a feature which could be utilized to determine its critical micelle concentration (CMC). A value of 3.98 x 10(-5) M was obtained and was observed to be slightly temperature dependent with a T-min of 25.35 degrees C. Fluorescence quenching experiments using 4-nitroaniline as a quencher were performed in order to determine the aggregation number which was found to be 42.0. The hydrodynamic radius of 21.91 Angstrom was obtained using data from viscosimetric experiments. These data, together with the Tanford and Einstein-Stokes relationships, were used to determine the micellar structure (spherical) and the diffusion coefficient (D = 0.97 x 10(-6) cm2/s), respectively. The Delta G of micellization for BDHC was determined to be -34.9 kJ/mol.