Ultrasonic relaxation studies of ternary and quaternary systems containing 2-butoxyethanol, water, decane, and cetyltrimethylammonium bromide

Abstract

Ultrasonic absorption measurements have been made in ternary microemulsions composed of oil (decane, DEC)-cosurfactant (2-butoxyethanol, BE)-water and quaternary microemulsions of oil (DEC)-cosurfactant (BE)-surfactant (cetyltrimethylammonium bromide, C/sub 16/TAB)-water in order to study the exchange processes of BE between the bulk phase and the large aggregates present in these systems. The studies were done in the frequency range 5-210 MHz and at temperatures between 25 and 45/degrees/C. The effect of salt (sodium chloride and calcium chloride) on the ultrasonic absorption parameters was also studied in the quaternary systems. The results of these studies show that there are two relaxation processes which are located at /approximately/10 and /approximately/60 MHz for the majority of systems investigated. In the ternary systems, both relaxation frequencies are observed to be independent of decane concentration up to a specific mole percent and then they gradually decrease with increasing concentration of oil until phase separation occurs. In the quaternary systems, the higher relaxation frequency decreases while the lower one is invariant with increasing concentration of decane. The salts do not appear to affect, significantly, the ultrasonic parameters for the quaternary systems. The temperature dependence of the relaxation frequencies in ternary systems was analyzed to give an estimate of themore » activation enthalpies for the relaxation processes. Values of 15-25 and 13-17 kJ mol/sup -1/ were obtained for the low- and high-frequency relaxation processes, respectively. Photon correlation spectroscopy (PCS) measurements were made in an attempt to obtain additional information on the nature and size of the aggregates present.« less