Development of New D,L-Methionine-based Gelators.

D,L-Methionine was chosen as a starting material for the preparation of a new gelator N-10-undecenoyl-D,L-methionylaminooctadecane (DL-Met-R-18). Three oligo (dimethylsiloxane)-containing gelators, DL-Met-R-18/Si-3 DL-Met-R-18/Si7-8, and DL-Met-R-18/Si14-159 were also prepared from DL-Met-R-18 by hydrosilylation reactions. Their gelation abilities were evaluated on the basis of the minimum gel concentration using nine solvents. Compound DL-Met-R-18 was able to gelate liquid paraffin and silicone oil, but it crystallized in most solvents. However, DL-Met-R-18/Si7-8 resulted to be the best gelator, gelling eight solvents at low concentrations. The results of gelation tests demonstrated that the ability to form stable gels decreases in the following order: DL-Met-R-18/Si7-8 approximate to DL-Met-R-18/Si14-15 > DL-Met-R-18/Si-3 >> DL-Met-R-18. The aspects and thermal stabilities of the gels were investigated using three-component mixtures of solvents composed of hexadecyl 2-ethylhexanoate, liquid paraffin, and decamethylcyclopentasiloxane (66 combinations). DL-Met-R-18/Si-3, DL-Met-R-18/Si7-8, and DL-Met-R-18/Si14-15 could form gels with all these mixed solvent combinations; particularly, DL-Met-R-18/Si7-8, gave rise to transparent or translucent gels. FT-IR spectra suggested that the formation of hydrogen bonds between the NH and C=O groups of the amides is one of driving forces involved in the gelation process. Aggregates comprising three-dimensional networks were studied by transmission electron microscopy. Moreover, the viscoelastic behavior of the gels was investigated by rheology measurements.