Extremely Slow Reaggregation Processes in Micelle Solutions. A Dynamic Light Scattering Study

Photon correlation measurements were performed on the dodecylpyridinium iodide/water system to yield the mean radius of micelles as a function of the time interval after a change in the temperature from 80 to 25 °C. Depending on the purification procedure applied to the sample, large aggregates, probably with dust particles as nuclei, may be formed after the temperature jump. Simultaneously, large micelles are also formed, the radius of which may reach four times the equilibrium value of the system. The micellar radius exhibits relaxation characteristics with extremely long relaxation times, reaching values up to several hours. Obviously, the nucleation of a sufficient number of micellar aggregates is hindered by the extremely unfavorable equilibrium concentration of submicellar-size intermediates. This leads to a strongly deviating nonequilibrium distribution with an excess of extra large micelles during the thermal equilibrium. Establishing the final equilibrium is then a very slow process, due to the low monomer concentration, which is maintained by the presence of the extra large micelles.

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