BEHAVIOR OF A SURFACE-ACTIVE CYANINE DYE IN WATER AND SURFACTANT SOLUTIONS

N-Cetyl-4-(p-N,N-dimethylamino)styrylpyridinium bromide (I) has been used as a probe to study the effect of hydrophobic chain in organising the dye molecule in water medium. (I) forms a condensed monolayer on water surface covering 65 angstrom 2/molecule. An L-L type of aggregation has been proposed on the basis of the calculated area of the molecule. A hyposochromic shift in the absorption of (I) in aqueous medium in the presence of CTAB (below CMC) suggests formation of a dimer. But above the CMC of CTAB, (I) forms aggregates with CTAB leading to a mixed micelle formation. However, in reversed micelle, a bathochromic shift is observed with increasing water concentration. This shift reveals a J-type aggregation of the dye at the interface.