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A series ofN-(n-alkylcarbamoyl)-l-amino acid amphiphiles with different amino acid head groups were designed and synthesised. The gelation abilities of these amphiphilic molecules were studied in toluene andp-xylene solvents. The hypothesis that steric crowding at the chiral head group destroys gelation ability of the amphiphile was examined. Indeed, besidel-alanine-based amphiphile, onlyl-serine andl-aspartic acid derivatives were found to gelate the organic liquids efficiently in the presence of a small quantity of water. The gels were characterised by a number of methods, including FT-IR, NMR and X-ray diffraction spectroscopy, scanning electron microscopy (SEM) and rheology. The SEM micrographs revealed three-dimensional networks of ribbon-like aggregates. The organogels were observed to be thermo-reversible in nature and have sufficient mechanical strength. The gels have gel-to-sol transition temperatures above the physiological temperature (310 K). [ABSTRACT FROM AUTHOR]

The major driving force for organogelationis known to be hydrogenbonding for gelators containing functional groups capable of forminghydrogen bond(s). In order to examine this, we have investigated thegelation behavior of two 4-(N-tetradecanoyl)aminohydroxybutanoicacid amphiphiles in a series of organic solvents and compared withthose of the corresponding unsubstituted amphiphile 4-(N-tetradecanoyl)aminobutanoic acid (C14-ABA). The gelationability of the nonhydroxyl amphiphile C14-ABA was foundto be better than the hydroxyl group substituted amphiphiles. An attemptwas also made to correlate gelation abilities of the amphiphiles withthe solvent polarity parameters. The driving force for the gelationwas studied by Fourier transform infrared and 1H NMR spectroscopy.The organogels were characterized by electron microscopy and XRD.The thermal stability of the gels was investigated by measuring thesol-to-gel transition temperature. Rheological measurements were performedin order to determine the mechanical stability of the organogels.The gelation ability and thermal and mechanical stability of the organogelswere correlated with the intermolecular hydrogen-bonding interactionsbetween amphiphile head groups. [ABSTRACT FROM AUTHOR]

Abstract: We report gelation behavior of a series of N-acyl-β-alanine (C n -β-Ala) gelators in a variety of organic liquids. The effect of alkyl chain length was studied to elucidate gelation mechanism. The gelation behavior of the C n -β-Ala gelators was compared with that of corresponding N-acyl-l-alanine (C n -l-Ala) derivatives. Unlike C n -l-Ala the C n -β-Ala gelators failed to gel aliphatic hydrocarbons and exhibit phase-selective gelation in the presence of water. The gelation ability of C n -β-Ala was observed to be poorer than C n -l-Ala gelators. Also C n -β-Ala organogels are thermally less stable, but they are observed to have higher mechanical strength than C n -l-Ala organogels. [Copyright &y& Elsevier]