What affects the degree of micelle ionization: conductivity study of alkyltrimethylammonium chlorides

The critical micelle concentration, cmc, and the degree of micelle ionization, β, of decyltrimethylammonium chloride (DeTAC), dodecyltrimethylammonium chloride (DTAC) and tetradecyltrimethylammonium chloride (TTAC) in water, 0.01 M, and 0.1 M NaCl solution were determined from the electrical conductivity data in the temperature range from 278.15 to 328.15 K. It has been found that cmc is decreasing with increasing surfactant chain length and increasing concentration of added NaCl, whereas the temperature dependence of cmc shows the typical U-shaped form with a minimum around (306 ± 3) K. Further, β is decreasing with lengthening the alkyl chain of surfactant and increasing with increasing temperature, but no distinct influence of added salt has been found actually. It can be concluded that the effect of electrolyte on micelle ionization is quite complex.