Dilute solutions, chromonics

The tendency for the molecnles of chromonic phases to aggregate into colnmns is present even in dilute solution where colnmn formation occnrs before a phase is formed. Althongh there may be a threshold concentration before aggregation begins to occur, there is no optimum column length and hence no critical concentration, with a further distinction being the absence of a Krafft temperature. Since the process of mesophase formation does not depend on the presence of flexible alkyl chains, there is no threshold temperature below which mesophases cannot form because the vital flexibility of the molecules has been frozen out. 

The tendency of chromonic molecules (Fig. 1) to aggregate into columns is present even in dilute solution (just as for amphiphile systems, where micelle formation occurs before a mesophase is formed). How-... 

The Aggregation of Chromonic Molecules in Dilute Solution and on Substrate Surfaces... 

There is then a sudden drop in the free energy as virtually all of the amphiphile molecules are incorporated into micelles, enabling their hydrophobic alkyl chains to be more or less completely shielded from the aqueous part of the phase. This leads to the familiar abrupt change in physical properties at the cmc. In chromonic systems there is also the aggregation of molecules in dilute solution before mesophase formation, but the pattern of association is different. The hydrophobic surfaces of the molecules cause them to aggregate in stacks like packs of cards. As these stacks grow, the fraction of the total hydrophobic surface area exposed to the aqueous part of the phase steadily falls, but there is no minimum free energy state, no cmc, and there is no structure directly comparable to the micelle [38]. 

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