Salt complexes of two-component N-acylamino acid diastereoisomers: self-assembly studies and modulation of gelation abilities

Abstract

The self-assemblies and gelation of various organic solvents by salt complexes of two-component N-acylamino acid diastereoisomers are described. The potent organogelator, N-(2-aminoethyl)-α-[-(1-oxoheptadecyl)amino]phenyl) propanamide, was mixed with various N-acyl leucines having different fatty alkyl chain lengths at a ratio of 1:1. In some cases, their complexation resulted in modulations of the current gelation abilities. When the l-form of the organogelator was used for mixing, the gelation ability appeared to be independent of the hydrophobic nature of the N-acyl leucine. This is not observed when the racemate form of the organogelator was used. Moreover, a minimum gelation concentration (MGC) in aromatic solvents as well as improvements of the gelation ability such as formation of a robust hydrogel in water, gelation of the R-propylene carbonate, and unexpected gelation of pyridine were observed. The supramolecular gels were analyzed by Fourier Transform-Infrared (FT-IR), 1H nuclear magnetic resonance (NMR) spectroscopies, and rheology analysis. The phase transition temperatures (Tg–s) were determined using differential scanning calorimetry (DSC). Homogeneity of the gel networks was observed by field emission scanning microscopy (FE-SEM) and transmission electron microscopy (TEM). The lamella structure was confirmed by X-ray diffraction (XRD).