Triggered formation of thixotropic hydrogels by balancing competitive supramolecular synthons

Abstract

Two component hydrogels have been obtained by formation of 1 : 1 complexes of bis(pyridyl urea)s with a range of dicarboxylic acids. The gels are thixotropic and undergo an assembly process in which short segments can reversibly assemble into an interconnected fibrous network. NMR and IR spectroscopic data suggest that the gelators form neutral gelator–acid complexes rather than salts. The use of dicarboxylic acids to trigger gelation in bis(pyridyl urea)s parallels analogous triggered gelation of metal ions and halogen bond donors in related systems.