l-Cysteine-DerivedAmbidextrous Gelatorsof Aromatic Solvents and Ethanol/Water Mixtures.

A series of l-cysteine-derived double hydrocarbonchainamphiphilic gelators l-(3-alkyl-carbamoylsulfanyl)-2-(3-alkylurido)propionicacid with different hydrocarbon chain lengths (C6–C16) wasdesigned and synthesized. These gelators efficiently gelate only aromaticsolvents. The gelation ability increased with the increase of chainlength up to C14, but then it dropped with further increase of chainlength. The C12 and C14 derivatives also gelled ethanol/water mixtures.The gels were characterized by a number of methods, including FT-IR,NMR, and XRD spectroscopy, electron microscopy, and rheology. Theamphiphiles were observed to form either flat lamellar or ribbonlikeaggregates in aromatic solvents as well as in ethanol/water mixtures.The gelation in all the solvents employed was observed to be thermoreversible.The gel-to-sol transition temperature as well as mechanical strengthof the organogels were observed to increase with the hydrocarbon chainlength. Both types of gels of C8–C16 amphiphiles have gel-to-soltransition temperatures above the physiological temperature (310 K).FT-IR and variable temperature 1H NMR measurements suggestedthat van der Waals interactions have major contribution in the gelationprocess. The gel-to-sol transition temperature and mechanical strengthof the organogels in ethanol/water mixtures was observed to be higherthan those of benzene organogel. [ABSTRACT FROM AUTHOR]