EXTREMELY SLOW REAGGREGATION PROCESSES IN MICELLE SOLUTIONS - A DYNAMIC LIGHT-SCATTERING STUDY

Photon correlation measurements were performed on the dodecylpyridiniu m iodide/water system to yield the mean radius of micelles as a functi on of the time interval after a change in the temperature from 80 to 2 5 degrees C. Depending on the purification procedure applied to the sa mple, 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 characte ristics with extremely long relaxation times, reaching values up to se veral hours. Obviously, the nucleation of a sufficient number of micel lar aggregates is hindered by the extremely unfavorable equilibrium co ncentration of submicellar-size intermediates. This leads to a strongl y deviating nonequilibrium distribution with an excess of extra large micelles during the thermal equilibrium. Establishing the final equili brium is then a very slow process, due to the low monomer concentratio n, which is maintained by the presence of the extra large micelles.