Structural variations in amphiphiles: Discoidal multivalent cations

Abstract

Fourteen cationic multipolar amphiphiles have been synthesized with pyridinium or trimethylammonium head groups. The hydrophobic cores are planar ring systems (benzene or triphenylene) to which two, three, four, or six decylene or undecylene alkyl chains are attached by ester linkages. The hydrophilic head groups are bound to the outer ends of the alkyl chains.The aggregation of the molecules in water into micelles and lyotropic liquid crystals has been studied. Hexagonal phases are preferred to lamellar phases by these amphiphiles and in more dilute solutions some of these muhipolar amphiphiles form cylindrical micelles.

Molecular concepts, self-organisation and properties of polysoaps

“…Thus solubilization studies appear to be more appropriate for CMC determinations but have been seldom performed. Interestingly, the CMC values assigned from conductivity and surface tension data level approximately at the level of the "dimers" [422,425] (Fig. 42), whereas the CMC value derived from solubilization data for a "hexamer" surfactant is lowered by at least a factor of 100 compared to the "monomer" [419].…”

“…Defined "oligomeric" surfactant structures obviously have stimulated the imagination of many colloid chemists, as a number of imaginative names were suggested for them: bola-surfactants [410][411][412], gemini-surfactants [413][414][415], tentacle molecules [416][417], octopus molecules [418], hexapus [419], multiarmed amphiphiles [420][421][422]. .…”

“…This is the more true, as the majority of the "tail end" structures represents "stars" [416,417,420,422,425,449] rather than linear or cyclic oligomers [418,419,423]. Most attempts to produce "head-type" trimers suffer from the poor water solubility of the products [450], but recently some water-soluble examples have been reported [427].…”

“…CMC-like transitions become less clear, in particular of studied by surface tension and conductivity measurements [416][417][418][419][420][421][422]425]. The reduction of the surface tension by such oligomers is often quite low [416-420, 422, 423, 425], and the shape of the plots of surface tension vs the logarithm of the concentration can be bizarre [417,425] though not necessarily for all systems studied [423].…”

Micellar and lyotropic behavior of three isomeric bola‐amphiphiles with pyridinium groups

“…for 2 u = i0.22 m N / m (l.3.10-'-3. 7. lo-' mol/l)] and much lower for concentrations above the CMC [ e .…”