APPARENT MOLAR VOLUME AND APPARENT MOLAR ADIABATIC COMPRESSIBILITY STUDIES OF ANESTHETIC MOLECULES IN AQUEOUS MICELLE SOLUTIONS OF CTAB ANDCTAC AS A FUNCTION OF SURFACTANT CONCENTRATION AND TEMPERATURE

Apparent molar volume and adiabatic compressibility properties of halo thane and isoflurane in aqueous micelle solutions of hexadecyltrimethy lammonium bromide (CTAB) and chloride (CTAC) have been studied as a fu nction of surfactant concentration and temperature. Specific conductan ce measurements of the micellar systems in the presence and absence of the additive molecules were used to estimate the effect of the solubi lized additives on the apparent degree of micelle dissociation. As wel l, H-1 T-1 relaxation and chemical shift studies of the micellized sur factant in the absence and presence of the additive were measured in a n attempt to obtain complementary data regarding the solubilization si tes of the additives in the micellar systems. The results show that th e degree of micelle ionization, the extent of hydration of the counter ions and of the head groups of the micellar systems, and the polarity of the anesthetic molecules play a role in the solubilization process. The inhalation anesthetics appear to be adsorbed in the head group re gion of the micelles, replacing water in this region in the case of th e more hydrated micelles. Also, they penetrate to sites nearer to the alpha- and beta-methylene groups of the surfactant hydrocarbon chains when head group sites become saturated or the additive is less polar.