Jeong Moo Lee

Micelles of surfactants and polymers are formed due to hydrophobic interaction. Water, as it were, pushes the molecules into the micelle, since its intermolecular interaction is greater than the dispersion interaction of hydrocarbon groups. If you examine micelles with cryoTEM, then you get information about micelles only at low water temperature. The temperature changed, so the micelles in the cryoTEM disappeared.

Dialysis does not need to be associated with your study. The dialysis time is determined by the surfactant concentration gradient. After a long time, the equilibrium concentration of the surfactant sets in, and micelles may disappear in the bag.

The dialysis method you show is for removing the small molecules from the interior of the bag while retaining the large molecules. In the case of micelles, the small molecules (monomers) and the micelles are in equilibrium. If you reduce the concentration of the small molecules by dialysis, the micelles will dissociate into monomers once the monomer concentration falls below the critical micellar concentration.

To increase the concentration of micelles without changing the concentration of monomers, you can use ultrafiltration. In this method, the solution is forced through a porous membrane either by gas pressure or by centrifugation. The membrane has holes of a certain size that is smaller than the size of the micelles but larger than the monomers. The risk of this method is that the micelles may aggregate due to compression against the membrane.

Another approach, going back to the dialysis bag, is to immerse the bag in an absorbent material to draw out some of the water. This will also draw out some of the monomers, of course, but because the volume inside the bag also decreases, the monomer concentration should not change substantially. Some useful absorbent materials are carboxymethylcellulose and dry gel filtration resin, such as Sephadex G-100 or Bio-Gel.