A surface-active merocyanine dye as a probe of micellar environments

The merocyanine dye 4-[2-(1-hexadecyl-1,4-dihydropyridin-4-ylidene)ethylidene]cyclohexa-2,5-dien-1-one has been synthesized, and its properties as a probe of micellar microenvironments have been investigated. The dye is solubilized by micelles, and its merocyanine terminus is accommodated in a polar environment. The u.v./visible absorption spectrum of the dye provides a measure of solvent polarity in this microenvironment, and provides information concerning the pH. Determination of the critical micelle concentration is conveniently achieved by noting the abrupt change in the absorption of the dye.