I have been doing some research on forming micelles that are formed by block copolymers. I want to know that if the concentration of the system get lower than cmc, will the micelles break up and disperse at molecular level in the solvent? I know that micelles formed by small molecules can break up as the concentration decrease, but for micelles formed by block copolymers, I can't be certain about it. does anyone have experiences on it? Thanks.
Block copolymer molecule depending on the solvent, the electrolyte can exist in the form of a coill and globule. In polymer physics, the coil–globule transition is the collapse of a macromolecule from an expanded coil state through an ideal coil state to a collapsed globule state, or vice versa. Globule is a micelle. So no need to increase the concentration and the need to find the conditions for phase transition coil into a globule.
Since you mention a CMC, the system is presumed to have a critical transition that is thermodynamic in nature, and therefore is reversible (not in the zero-entropy sense, but in the sense that you can revert back to a prior morphology by changing the concentration back). So the answer is yes. Now, that's especially the case for systems that are ergodic (for example, block copolymers in the melt state, BCP blended with a homopolymer, or even BCP dissolved in a small molecule solvent). But if you have a non-ergodic system - for example, your BCP has a glassy block, and you change the concentration back below the CMC but at a temperature below the Tg of the glassy block, then your micelles may persist.
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