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Based on the principle of supramolecular preorganization, a new type of oligofunctional amphiphile, of which compounds 1-4 are representative structures, has been designed and synthesized. The typical feature of their structure is a highly rigid and geometrically well-defined central unit composed of ethynylene substituted aromatic spacers with different numbers of amphiphilic segment groups (also of a rigid geometric design) attached to it. The molecules form well-defined Langmuir films when spread from a solution at the air/water interface or when a 10(-4) M aqueous CaCl2 solution was used as the subphase. By analysis of the surface pressure-surface area (pi-A) isotherms, information on the packing behavior and orientation of the amphiphilic molecules depending on the molecular structure could be obtained. Morphological characterization of the dynamic process of monolayer compression at the air/water interface was carried out by Brewster angle microscopy, illustrating several phase states visualized as snap shots. Thin monolayer films produced on a 10(-4) M aqueous CaCl2 subphase can be transferred to a mica solid support by the Langmuir-Blodgett technique. Tapping mode atomic force microscopy reveals a surface topography of the monofilms composed of 1 and 3 that differ in roughness and also in the properties of elasticity, hardness and adhesive strength. X-Ray crystal structure analysis of three relevant intermediate compounds of the synthesis were successfully determined giving an indication of the potential structural features inherent in the new amphiphiles.

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New 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 comparision, 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.

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