Supramolecular Gelation of Triphenylamine Bis-Urea Macrocycles in Toluene

Abstract

Herein, we investigate the supramolecular gelation behavior of a dendronized triphenylamine bis-urea macrocycle (1) in toluene in the presence and absence of sulfoxide chain stoppers. Macrocycle 1 assembles in the sol phase through intermolecular hydrogen bonding interactions, spontaneously transitioning into a gel state when left undisturbed at room temperature. In toluene, 1 displays a critical gelation concentration of 0.066 wt %, classifying it as a supergelator. Furthermore, it exhibits a thermoreversible gel−sol phase transition as well as a thixotropic behavior. Temperature-dependent 1 H NMR spectroscopy is employed to probe the sol phase assembly of 1 with the size variations at different temperatures assessed by 2D DOSY. Rheological experiments at 10 °C were used to measure gelation response to mechanical stimuli. An amplitude sweep test highlights a linear viscoelastic region. Additionally, the self-healing behavior of gel 1 was verified through a series of strain cycles, where it showed complete recovery. Addition of chain stoppers 10% vs 1 of dimethyl sulfoxide (DMSO) and diphenyl sulfoxide leads to weaker gels with smaller differences between the storage and loss moduli. Rheological analysis revealed slower/partial recovery for the gel containing chain stoppers. Gels assembled from macrocyclic building blocks may retain homogeneous binding cavities and channels offering novel functional properties.