Regarding the pesticide industry it is a very common and general application of calcium dodecylbenzene sulfonate’s (CaDDBS) usage in the composition of emulsifiable concentrates The calcium dodecylbenzene sulfonate (anionic emulsifier) is insoluble in water but well soluble in water-immiscible solvents such as butanol or even xylene etc.. The CaDDBS is apparently present in these solvents in the form of inverted micelles.
During emulsification, the free surfactant molecules (after breaking of micelles) are placed on the surface of the droplets and the molecules adsorbed there. In the case of CaDDBS two dodecylbenzene sulfonic acid groups belong to one calcium ion. Does dissociation occur or not (since CaDDBS is virtually completely insoluble? Will real hydrophobic anion form (or dissociation is very limited? How can we schematically draw the structure of the adsorption layer? It seems that the structure of Ca-DDBS is more convenient to provide the water-in-oil macro-emulsion but in the practice formulation chemist is mainly using CaDDBS to obtain oil-in-water emulsion . Isn't the Bancroft rule true in this case?
It might be a very complicated system but if the vision is about an inverted micelle, I would think there is no real dissociation. If at all, most probably there are different ionic pairs present, perhaps contact ionic pairs or partially hydrated with water in the micelles (how much water? that is also a question which may be experimentally addressed). It is difficult to figure out a real dissociation in the heart of the micelle, and also, it is difficult to figure out an essential ionization with multiple calcium ions present in the micelle interior. Just a thought...
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