What factors influence the upper size limit of micelle's?

Is there an inherent size at which micelle's cannot grow larger in volume?
I have been trying to find a quantifiable method of measuring a size limit with all the variables that affect micelle formation and growth (solvent polarity, temperature, etcetera), but I've failed at finding a good resolute answer. Was wondering how one could compute a result for this.




Micelles form from individual surfactant molecules , beginning at the CMC (critical micelle concentration), which varies for different surfactants, but is in the range of about 100 ppm (Ref 1).


[![enter image description here](https://i.stack.imgur.com/QTj6r.png)](https://i.stack.imgur.com/QTj6r.png)


At one end of the scale, sodium octyl sulfate (mw = 232) requires 0.13M to form micelles because it is soluble enough to exist surrounded by water molecules until there are enough other octyl sulfate anions nearby that the octyl groups associate. The surfactants with lower CMC associate more at lower concentrations.


The first micelles will be small, but grow larger as the concentration of surfactant increases. As long as they stay dispersed (Brownian motion), they might as well be soluble. However, if the concentration of the surfactant increases, it will become a separate phase, a separate layer (usually floating). Some dispersible surfactants (like polyethylene oxide surfactants) have a cloud point, where raising the temperature decreases the solubility to the point where micelles prefer agglomeration rather than dispersion in water. Just below the cloud point is where the micelles would be largest. Above that temperature, if two of these very large micelles collide, they begin forming the separate (floating) phase.


Stirring a concentrated surfactant solution with high shear would generate some very large (but unstable) globs which resemble micelles - not unlike making an oil-in-water emulsion. But this is probably not what you want.


Even with surfactants without a cloud point, increasing the concentration to just below the solubility limit would create the largest possible micelles.


Surfactant solutions (even below the cloud point) show a Tyndall effect, scattering of light. At the concentrations producing large micelles, the micelle size would be significantly larger than the wavelength of light, and a drop of the solution between glass slides could be examined with a good microscope. If you insure the micelles are not squashed, a good estimate of diameter, and thus volume, could likely be obtained.


An off-the-top-of-my-head estimate for the largest possible micelle volume would be the volume of a particle with the density of the surfactant that can be suspended indefinitely by Brownian motion against settling by gravity. Smaller particles would be more stable; larger particles would coalesce. Thickening the water with gums like xanthan could stabilize much larger micelles. A surfactant with density very close to H2O would also confer greater stability (in H2O) to large micelles. And lower gravity (space station?) might work too.


Ref 1. <https://en.wikipedia.org/wiki/Critical_micelle_concentration>


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