Diffusion-Controlled Reactions in Micellar Systems

M. Tachiya and A.V. Barzykin
[Mat. Res. Soc. Symp. Proc. , Vol.366, pp.365-376, 1995]

Reaction kinetics in micellar solutions are studied theoretically with an emphasis on diffusion-controlled luminescence quenching. Different spatial arrangements of reactants within individual micelles are analyzed and a general method for treating diffusion-controlled reactions in a finite volume employing an effective potential approximation is developed. Several models are considered for the exchange of reactants between micelles including migration mediated by the bulk phase and successive multiparticle hopping through transient channels connecting micelles during their sticky collisions. These results are combined in a general stochastic theory of reaction kinetics in micellar solutions with exchange (Fig. 1). The theory is further extended to reactions in clusters of micelles using a continuous time random walk approach. Once the principal features of micellar kinetics are understood, one can extract important structural and dynamic information on the aggregates and their guest molecules by analyzing suitably designed experiments.

Fig. 1. Time decay of the excited probe survival probability F(t) for the collisional exchange mechanism of quenchers (Ñ) and probes (---) with k_e/k_q = 2 and (k + k_p) tau_c= 0.1, 05, and ° (the number attached) for the Poisson distribution of quenchers among the micelles with the average n=2. The decay for infinitely fast and infinitely slow migration, as compared with quenching is also included (- á -). The decay for a one-particle quencher migration mechanism with k_-/k_q = 0.2 (ááá) should be compared to the curve with k_e/k_q = 2 and ktau_c= 0.1. Multiparticle hops still affect the long time behavior. Note that self-decay is omitted.