The impact of the isomerism of peptide mimetics on their assembly and properties: quick and onsite gas phase detection of acids and alcohols

Abstract

The effect of isomerism on the structure, self-assembly and properties of two peptide mimetics has been investigated. These peptide mimetics contain m-aminobenzoic acid, p-aminobenzoic acid and N,N′-dicyclohexylurea. From X-ray crystallography, it is observed that the p-isomer adopted a kink-like conformation stabilized by C–H⋯π interactions and formed a supramolecular anti-parallel duplex and layer by layer sheet-like structure in higher order assembly. However, only the m-isomer formed sonication responsive gels in different hydrocarbons such as hexane–EtOAc (19 : 1), diesel, kerosene, body oil and coconut oil. From rheology experiments, the gel was found to have physical cross-links and is elastic in nature. The FE-SEM images depicted that the m-isomer exhibited nanofiber network morphology, whereas the p-isomer exhibited polydisperse microsphere morphology. The gel was found to be highly sensitive to alcohol vapours, although the kinetics become much slower from methanol to ethanol to isopropanol. The gel is also very responsive to acid vapours like HCl.