Micelle formation of cationic detergent solution at high pressures

Abstract

The effect of pressure on the critical micellar concetration (c. m. c.) of the aqueous solution of cationic detergents i.e. dodetyl ammonium chloride (DAC), dodecyl trimetylammonium chloride (DTAC) and dodecyl benzyldimethylammonium chloride (DBAC) has been investigated by the conductivity measurement. The c. m. c. of DTAC and DBAC increases with increasing pressure up to about 1000 atm and then it gradually decreases at higher pressures. The DAC solution shows a peculiar behavior. At about 2300 atm its specific conductivity decreases sharply. Assuming the equilibrium between single detergent ions and micelle ions, the partial molal volume change caused by micelle formation is discussed. At 1 atm the ΔV of the above mentioned three substances is about +3 cc/mole at 25℃. Above 1000 atm the sign of ΔV changes to minus.