Characterization of Fluorescent Surfactant Aggregates by Fluorimetric and Viscosimetric Techniques

Article abstract of DOI:10.1007/BF00807588

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 × 10^-5 M was obtained and was observed to be slightly temperature dependent with a T_min of 25.35°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 A 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 × 10^-6cm²/s), respectively. The ΔG of micellization for BDHC was determined to be -34.9kJ/mol.