To the Mechanism of the Formation of Micelles in Sodiumdodecylsulfate(SDS)‐solutions

Kinetic measurements using relaxation techniques were carried out with solutions of pure Sodiumdodecylsulfate (SDS) and of SDS which had different surfactants added (Dodecylalcohol (DOH), Sodiumtetradecylsulfate (STS), Dodecylpyridiniumchloride (DPCI)). The results have shown, that some of the earlier investigations on SDS were effected, probably by the presence of small amounts of Dodecanole (DOH), or homologs of SDS, for example Sodiumtetradecylsulfate (STS). Two relaxation times could be measured in the pure solutions. The faster relaxation time was dependent on the concentration of the solution, while the slower one was almost independent on the total concentration c o . For both processes it was possible, to measure a relaxation‐time at the critical micelle concentration (cmc), from which rate constants for the dissociation of a monomer out of the micelle and the disappearance of a micelle were determined. The rate constants for the processes A n +1 → A n + A and A n → nA are at 20°C 1.9 · 10 4 s −1 and 900s −1 respectively. With the addition of small amounts of Dodecylpyridiniumchloride (DPCl) a third relaxation time could be observed, which was associated with the formation of mixed micelles. The rate constant for the decomposition of a mixed micelle with a single molecule of DPCl in the micelle was determined to 13.8s −1 (at 20°C).