Tethering of long‐chain amino acids to a rigid aromatic core—A new type of preorganized surfactants acting as flotative agents

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AbstractNew oligofunctional surfactants prepared from ethyl 2‐aminododecanoate hydrochloride and positional isomers of aromatic acid di‐ and trichlorides via amide bond formation, including also the monofunctional compound of comparison, have been synthesized. Surface properties of the new compounds, in particular critical micelle concentration (CMC), surface tension at the CMC, effectiveness, and maximum surface excess, were determined. Moreover, their effectiveness at flotation using the model mineral fluorite was studied. We found that the surfactant parameters clearly depend on the number and position of the amphiphilic subunits attached to the aromatic core. We also found that a bundling of amphiphilic subunits, as performed, is profitable in the flotation of fluorite and that effects of preorganization due to the proximity and geometric grouping of the amphiphilic subunits are of importance. As a rule, the more amphiphilic subunits are included in the surfactant structure, the more efficient is the collecting agent, involving approximate enhancements of fluorite flotation by powers of 10 when going from mono‐ to bi‐ and trifunctional surfactant analogs, respectively. Nevertheless, the surface properties of the newly synthesized surfactants do not directly correlate with the flotation data, which makes relations between surfactant structure and efficiency of fluorite flotation at the current stage of development difficult to determine. Future studies relating to this problem are suggested.