Synthesis of triphilic, Y-shaped molecular surfactants

Novel multiphilic molecules comprising three chains with antagonistic affinities have been synthesized. These ‘triphilic’ surfactants (FnHmEOy) contain a perfluorinated arm (Fn=C_nF_2n+1), a hydrocarbon arm (Hm=C_mH_2m+1), and a methyl-caped, poly(ethylene glycol) arm (EOy=CH₃(OC₂H₄)_yO). These moieties have variable lengths (n=5 or 7, m=8, 10, or 14, and y=2-7) and are interconnected in a Y shape; hence, each unit is directly connected to the other two. The key intermediates in the synthetic route are 3-F-alkyl-3-alkyloxypropanoic acids, on which the polar EOy chain is subsequently grafted. Monodisperse methyl-caped diethylene glycol (EO2) and triethylene glycol (EO3) led to the corresponding monodisperse triaffine surfactants. In parallel, a library of five F5H10EOy triaffines (y=3-7) has been obtained simultaneously when starting from the polydisperse methyl-caped poly(ethylene glycol) MPEG 350. Separation of pure individual compounds was achieved through column chromatography on silica gel. The relative concentration of the Z and E isomers has been quantified in the reaction mixtures of the intermediates and final products by ¹H NMR (Z largely predominant). Several products have been obtained in their isomerically pure form. Chemical characterization (¹H, ¹³C, and ¹⁹F NMR, elemental analysis) was consistent with the expected structures.