β-cyclodextrin (β-CD) induced aggregation and micelle formation of cetyltrimethylam-mnium broAnde (CTMAB) in aqueous solution is demonstrated by the dual fluorescence of p-N, N-dAnethyladrinobenzoic acid (DMABOA) typical of the twisted intramolecular charge transfer (TICT). The locally excited (LE) state of DMABOA is proved to have the characteristic of intramolecular charge transfer (ICT) with a polarity higher than that of ground state but lower than that of TICT state. The peak positions of the two fluorescence bands and theiI intensity ratio are employed to probe the interaction of β-CD with CTMAB. It is conc1uded that β-CD induces CTMAB aggregation as well as Ancelle formation and may change Ancelle structure. The results also indicate that TICT in aqueous solution may be affected by the anisotropy or viscosity of the medium,increasing viscosity disadvantaging the TICT process.
The effects of aliphatic alcohol on the twisted intramolecular charge transfer (TICT) of p-N, N-dimethylaminobenzoic acid (DMABOA) in cetyltrimethylammonium bromide (CTMAB) micelle were examined by the TICT-typical dual fluorescence. The introduction of aliphatic alcohol (CnH2n+10H, n=1, 2, 3, 4, 6, 8, 14, 16, 18) to CTMAB Ancellar solution does not change the positions of the dual fluorescence bands of DMABOA,but results in a decrease in the fluorescence intensities with that of the longer-wavelength TICT band (a band) more repidly, the latter is demonstrated by a linear decrease of the fluorescence intensity ratio of a band to b band (shorter-wavelength normal band) with the concentration of the alcohol added. The logarithm of the absolute value of the linear slope is positively linearly correlated with the carbon number(n) of the alkyl chain in the alcohol molecule when the chain is relatively short (<8), whereas a negatively linear correlation is observed when the chain length (n=14, 16, 18) is comparable with that of CTMAB. In pure aqueous solution, the intensities and positions of the dual fluorescence bands are not varied by the same concentration of added alcohol. The decrease of the charge density of micellar surface due to the solubilization of alcohol in micelle is considered to be the cause of the alcohol effects on the TICT in charged micelle.
