ALKANEDIYL-ALPHA,OMEGA-BIS(DIMETHYLALKYLAMMONIUM BROMIDE) SURFACTANTS.4. ULTRASONIC-ABSORPTION STUDIES OF AMPHIPHILE EXCHANGE BETWEEN MICELLES AND BULK PHASE IN AQUEOUS MICELLAR SOLUTIONS

The critical micelle concentrations (cmc's) of two gemini surfactants, the propane- and hexanediyl-alpha,omega-bis(octyldimethylammonium bro mide), referred to as 8-3-8 and 8-6-8, have been determined by spectro fluorometry, ultrasonic absorption, and electrical conductivity measur ements. The isothermal volume change upon micellization of 8-6-8 has b een obtained from density measurements. The kinetics of the exchange o f 8- 3-8 and 8-6-8 between micelles and bulk phase has been investigat ed by the ultrasonic absorption relaxation method in the concentration range from slightly below cmc to about 2 cmc. All the solutions inves tigated showed that in the frequency range 0.5-85 MHz a single relaxat ion process is associated with the exchange equilibrium as in the case of conventional surfactants. It therefore appears that the two alkyl chains of gemini surfactants exit from and enter into the micelles sim ultaneously. The rate constants for these processes are close to those found for conventional cationic surfactants of similar nature and hav ing nearly the same cmc as the gemini surfactants.