Characterization of non-ionic surfactant aggregates by fluorometric techniques

Steady-state and nanosecond time-resolved studies have been carried out on the fluorescence quenching of excited pyrene by N,N-dibutylaniline in an aqueous solution of non-ionic micelles of the six Tritons, (oxyethylene)(m)-p-(1,1,3,3-tetramethylbutyl)phenyl ethers with in ranging from 8 to 70. The aggregation numbers and the rate constants of intramicellar quenching have been determined. The critical micelle concentrations of investigated Tritons were determined using the dependence of the fluorescence spectrum of pyrene on the microenvironment. The local polarity was obtained from the intensity ratio of the first to the third peak (I-1/I-3) in the fluorescence spectrum of pyrene. The microviscosity of the micellar core was estimated to be about 200 cl? at ambient temperature on the basis of fluorescence spectra of 1,3-bis(1-pyrene)propane, from the excimer to the monomer emission intensity ratio using the calibration curve determined for a number of solvents of known viscosities. (C) 2002 Elsevier Science B.V. All rights reserved.