Absorption and emission studies of solubilization in micelles. Part 1.—Pyrene in long-chain cationic micelles

Abstract

The monomer and excimer fluorescences of pyrene in dodecyl- and hexadecyl-trimethylammonium bromide micelles have been studied over the temperature range 297 to 325 K. An analysis of the quantum yield changes with concentration yields (a) values of the critical micellar concentrations, (b) the distribution of pyrene amongst the micelles, and (c) the rate of excimer formation and thus the diffusion of pyrene molecules within a micelle. The interior of the micelle appears very rigid to the pyrene molecules at low temperatures, but as the temperature increases it approaches a condition very similar to the corresponding hydrocarbons, dodecane and hexadecane. The high viscosity experienced by the pyrene molecules at low temperature is confirmed by spectroscopic parameters in absorption and emission studies.