EFFECT OF AROMATIC SOLUBILISATES ON THE SHAPE OF CTABR MICELLES

The locus of solubilization of some substituted and nonsubstituted aromatic molecules in hexadecyltrimethylammonium bromide (CTABr) micelles was determined by comparing the UV spectra of the aromatic compounds in the micelles and in solvents of various polarity. The polarity of the micellar microenvironment of these solubilisates increases in the order 1,4-di-tert-butylbenzene < isopropylbenzene < ethylbenzene < toluene < benzene congruent-to naphthalene congruent-to anthracene. The solubilized molecules thus distribute according to their own polarity between the highly nonpolar interior and the relatively polar interfacial region of a micelle. In the same order solubilization favors the axial growth of rodlike micelles of CTABr and decreases the degree of counterion association at higher KBr concentrations (0.1 and 0.2 mol L-1) as determined by viscosity measurements.