CHARACTERIZATION OF FLUORESCENT SURFACTANT AGGREGATES BY FLUOROMETRICAND VISCOSIMETRIC TECHNIQUES

A combination of fluorimetric and viscosimetric methods was used to ch aracterize 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 concentratio n (CMC). A value of 3.98 x 10(-5) M was obtained and was observed to b e slightly temperature dependent with a T-min of 25.35 degrees C. Fluo rescence quenching experiments using 4-nitroaniline as a quencher were performed in order to determine the aggregation number which was foun d to be 42.0. The hydrodynamic radius of 21.91 Angstrom was obtained u sing data from viscosimetric experiments. These data, together with th e Tanford and Einstein-Stokes relationships, were used to determine th e micellar structure (spherical) and the diffusion coefficient (D = 0. 97 x 10(-6) cm2/s), respectively. The Delta G of micellization for BDH C was determined to be -34.9 kJ/mol.