Low molecular weight gelators for organic fluids: Gelation using a family of cyclo(dipeptide)s

Simple cyclo(dipeptide)s consisting of diverse amino acids are able to cause physical gelation in a wide variety of organic fluids, including edible oils, glyceryl esters, alcohols, and aromatic molecules. Minimum gel concentrations, FTIR spectroscopy, NMR spectroscopy, and electron micrograph are used to characterize gel phenomenon, The intermolecular hydrogen bonding between N-H and C=O in cyclo(dipeptide)s plays an important role in gelation. FTIR and X-ray diffraction data suggest that the aggregate responsible for gel is an assembly of hydrogen-bonded molecular ladders, which are initially formed from numerous molecules through intermolecular hydrogen bonding. The ladder-like aggregates are intertwined and interlocked, and finally immobilize organic fluids, The gelation ability is discussed in connection with the three-component solubility parameters of solvents. (C) 2000 Academic Press.