Micelles sphere to rod transition

The experimental decays from the infinite rods at high salt concentrations in Fig. 4 fit well to the 1-D model. The same model has been used in several investigations of the sphere-to-rod transition and to determine the diffusion coefficients of the probe and quencher in rodlike micelles. However, equations based on other assumptions could fit the experimental data about equally well there is no distinctive feature in the decay that points to the 1-D case. Often one can reject alternative models due to unreasonable values for estimated parameters. A 2-D model, for example, would probably also fit well but would result in too low a value of the diffusion coefficient. Numerical studies demonstrated that 2-D and (with consideration of transient effects) 3-D models generally fit well to 1-D data but with unreasonable values suggested for the parameters, whereas a decay curve from a 2-D structure does not fit to a 1-D model [15]. 

Missel, RJ., Mazer, N.A., Carey, M.C., and Benedeck, G.B., Thermodynamics of the sphere-to-rod transition in alkyl sulfate micelles, in Solution Behavior of Surfactants, vol. 1, Plenum Press, New York, 1982, p. 373. 

From experiments of this type it is possible to draw conclusions about the location of the solubilized molecules in the micelles since the counterion relaxation is sensitive to the charge density at the micellar surface. It could, in the case considered, be deduced that hexanol, benzene and N,N-dimethylaniline, which cause a marked lowering of the relaxation rate at high concentrations, are mainly solubilized at or near the interface between the micelle and the intermicel-lar solution. Cyclohexane, which does not affect counterion relaxation, appears to be located in the micellar interior. Furthermore, it was deduced that the first three compounds promote the sphere-to-rod transition, whereas no shape alteration is induced upon solubilization of cyclohexane [Z21],... 

Oosawa emphasized the nucleation of the helix with n = 4 that appeared to best describe the experimental data for actin (cf. Section III.B). However, helix nucleation by critical nuclei having n smaller or larger than 4 is also described by Oosawa s theory. Recent work has considered the model with n = 2 for the G F transformation [44] (see also [41]). In fact, the scheme in Figure 7(b) has general validity for a host of nucleation processes in solution including, for instance, the nucleation of spherical micelles and their sphere to rod transition (cf. Section II.A.3) [13]. 

---