Organogel formation by coaggregation of adaptable amidocarbamates and their tetraamide analogues.
Mixtures of derivatives of Hanabusa's bolaamphiphilic amidocarbamates containing two Z-valinyl subunits and aliphatic spacers that range from ethylenic to octamethylenic are able to form organogels. A coassembly of them is observed in their acetonitrile and toluene gels; namely, the concentration of a given compound at which a gel is formed is lowered by the presence of equimolar quantities of any other compound in the series. The aggregates were studied by wide-angle X-ray diffraction (WAXD) and the results can be rationalized if the gel fibers are formed by supramolecular copolymers. NMR studies reveal that in solution these molecules adopt folded conformations containing intramolecular H-bonds, but IR studies indicate that these are not present in their aggregates. Additionally, analogues of the amidocarbamates obtained by replacement of the carbamate functionality by amide have been shown to behave in a similar way. For these molecules it can be shown that the central aliphatic subunit is not completely extended in the conformations present in the aggregates according to IR and WAXD studies. The tetraamide-type compounds described are robust organogelators that form gels in a variety of organic solvents with good thermostability and present improved feasibility for the synthesis of envisaged functional organogelators.
Escuder
Beatriu
B
Departament de Química Inorgànica i Orgànica, Universitat Jaume I, 12071 Castelló, Spain. escuder@qio.uji.es
Martí
Santiago
S
Miravet
Juan F
JF