Novel resorcinarene-based pH-triggered gelator

Iminodiacetate resorc[4]arene is shown to produce gels that are pH-reversible. The gels formed are clear and stable to inversion. (The gels are not stable above a certain temperature, which varies with concentration.) When the pH of an iminodiacetate resorc[4] arene solution (concentration > 7.6 mM) is lowered to below 2.5, which is near one of the K-a values of the molecule, the dissolved molecules aggregate and cause gelation of water. H-1 NMR showed that at the pH of gelation a change occurs in the chemical environment of the iminodiacetate group. Scanning electron microscopy showed that the gel is composed of long strands that interweave and create a molecular mesh.