Aggregation, wettability and radical scavenging activity of choline based ionic liquids in aqueous solution

Abstract

Nowadays, choline-based ionic liquids have been predominantly studied compared to other imidazolium, pyrrolidinium or pyridinium based ionic liquids due to low toxicity, biocompatibility, and biodegradable nature. The knowledge of the thermodynamic and interfacial properties for choline based ionic liquids (Cho-ILs) are now coming under scrutiny due to their importance in specific designing for several chemical processes and performance in specific applications. The current study explores the physicochemical properties of a series of Cho-ILs, which were synthesised by adopting a simple, economic, clean, and environmentally benign method. The synthesised Cho-ILs were characterised by Fourier transform infrared (FT-IR), NMR, and thermogravimetry assessment. Their surface activity along with aggregation behaviour was investigated by tensiometry, conductometry, UV-Vis spectroscopy. Cho-ILs displays a decreasing critical micelle concentration (cmc) with increasing alkyl chain on cation with lamellar shaped micelle formation. The antioxidant activity of synthesised Cho-ILs was studied using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assays. Further, concentration dependent surface behaviour of Cho-ILs was investigated by contact angle study to determine the wetting and spreading property which could help to understand the comparative adsorption and diffusion rates with possible interactions in desired applications.