Self-Healing Hydrogel from a Dipeptide and HCl Sensing

Ordered self-assembly of small organic molecules may induce novel properties in a supramolecular arrangement and can act as advance functional materials. This paper discusses the development of a new stimuli-responsive dipeptide hydrogelator containing l-phenylalanine and α-aminoisobutyric acid (Aib). The dipeptide Boc-Phe-Aib-OH, on addition with three equivalent of sodium hydroxide and water, transformed into a robust hydrogel. The transparent hydrogel is self-healing in nature. The instant gelation is highly selective toward sodium hydroxide and does not need any sonication or heating-cooling cycle. The thixotropic nature of the gel has been confirmed by rheological step-strain experiments at room temperature. Moreover, in the oil-water mixture, the compound exhibits phase-selective gelation. When the gel cylinder is cut into pieces, it does not conduct electricity, but once self-healing occurs, it conducts electricity. The diffusion of rhodamine 6G through the hydrogel indicates the dynamic nature. The hydrogel is highly sensitive toward HCl, that is, in the presence of HCl vapor, the gel becomes deformed.