Formation and properties of supramolecular hydrogels based on 1,2,4,5‐benzene tetracarboxylic acid and 2‐amino‐3‐hydroxy pyridine

Abstract On the basis of 1 H NMR analysis of the model complexes formed from ortho‐, meta‐, and para‐phthalic acid with 2‐amino‐3‐hydroxy pyridine (AHP), it was found that the two carboxyl groups located at the ortho position of the benzene ring more easily interact with AHP than those at meta‐ and para positions. A series of gelators (defined at G1–G5) were prepared from 1,2,4,5‐benzene tetracarboxylic acid (BTCA) and AHP at different molar ratios, and their structures were analyzed by 1 H NMR and FT‐IR. The gelation performances of the gelators were investigated in details, which indicated that G3 formed at the BTCA/AHP molar ratio of 1.0/2.3 possessed the shortest gelation time, the lowest minimal gelation concentration (MGC), and the highest maximal gel‐to‐sol dissociation temperature ( T gel ). The xerogels were analyzed by SEM and powder X‐ray diffraction, especially, the single crystal of G1 obtained directly from the gelling solvent showed complicated hydrogen bonded networks which were a direct evidence to explain the connecting network of the molecules. Based on this, the gelation properties were discussed. The relationship between the structures and properties of the gels is helpful for understanding the gelating mechanism and designing new gelators. Copyright © 2009 John Wiley & Sons, Ltd.