Abstract

Water/n-propanol/cetyltrimethylammonium bromide/allylbenzene micellar systems were formulated. The ratio (w/w) of n-propanol/
cetyltrimethylammonium bromide equals 2/1. The extent of the micellar region as function of temperature was determined. The micellar
systems were characterized by the volumetric parameters, density, excess volume, ultrasonic velocity and isentropic compressibility. The
micellar densities increase with the increase in the water volume fraction. Excess volumes increase with the water volume fraction and
temperature. Ultrasonic velocities increase with water volume fraction up to 0.8 then decrease. Ultrasonic velocities increase with
temperature for water volume fractions below 0.8 and increase for water volume fractions above 0.8. Isentropic compressibilities decrease
with the water volume fraction up to 0.8 then increase. Isentropic compressibilities increase with temperature for water volume fractions
below 0.8 and decrease for water volume fractions above 0.8. Structural transitions from water-in-oil to bicontineous to oil-in-water occur
along the micellar phase. The particle hydrodynamic diameter of the oil-in-water micellar systems decrease with temperature. In the diluted
region nanoemulsions systems were observed.

Key words: phase behavior, ultrasonic velocity, density, isentropic compressibility, hydrodynamic diameter; cetyltrimethylammonium bromide, allylbenzene, n-propanol, water