Organogelation through self-assembly of low-molecular-mass amphiphilic peptide

Development of supramolecular soft materials using naturally occurring precursors is of great interest. The present work reports the development of an amphiphilic peptide based low molecular weight (LMW) organogelator comprising of L-phenylalanine, L-lysine and tert-butyloxycarbonyl (Boc) protected 6-amino caproic acid. The peptide molecule is capable of gelating a wide range of aromatic and aliphatic organic solvents like benzene, toluene, ethyl acetate, tetrahydrofuran, chloroform and many others. The prepared organogels were thermoreversible in nature. The morphology of this organogelator was characterised by transmission electron microscopy (TEM). Morphological studies of the xerogels have revealed the formation of three dimensional (3D) self-assembled fibrillar networks (SAFINs). Involvement of different non-covalent interactions like hydrogen bonding, hydrophobic, pi-pi and van der Waals interactions in supramolecular gelation is studied by circular dichroism, X-ray diffraction, FTIR, photoluminescence spectroscopy, temperature dependent NMR and 2D NOESY experiments. Importantly, the mechanical strength of the organogelator in various solvents is found to be very high and the storage modulus value varies from 5000 to 45 000 Pa. Interestingly, this organogelator exhibits phase selective gelation by solidifying both aromatic and aliphatic organic solvents from their mixtures with water. Furthermore, the corresponding xerogel has an excellent ability of removing toxic dyes from water within a short period of time.