Natural Deep Eutectic Solvents Based on Choline Chloride and Phenolic Compounds as Efficient Bioadhesives and Corrosion Protectors

[EN] Natural deep eutectics solvents (NADES), owing to their high solvation capacity and nontoxicity, are actively being sought for many technological applications. Herein, we report a series of novel NADES based on choline chloride and plant-derived polyphenols. Most of the obtained phenolic NADES have a wide liquid range and high thermal stability above 150 degrees C. Among them, small-sized polyphenols, like pyrogallol, vanillyl alcohol, or gentisic acid, lead to low-viscosity liquids with ionic conductivities in the order of 10(-3) S cm(-1) at room temperature. Interestingly, polyphenols possess valuable properties as therapeutic agents, antioxidants, adhesives, or redox-active compounds, among others. Thus, we evaluated the potential of these novel NADES for two applications: bioadhesives and corrosion protection. The mixture of choline chloridevanillyl alcohol (2:3 mol ratio) and gelatin resulted in a highly adhesive viscoelastic liquid (adhesive stress approximate to 135 kPa), affording shear thinning behavior. Furthermore, choline chloride-tannic acid (20:1) showed an extraordinary ability to coordinate iron ions, reaching excellent corrosion inhibitive efficiencies in mild steel protection.This work was supported by Marie Sklodowska-Curie Research and Innovation Staff Exchanges (RISE) under Grant Agreement No. 823989 "IONBIKE". The financial supports received from CONICET and ANPCyT (Argentina) are also gratefully acknowledged. Liliana C. Tome is grateful to Fundacao para a Ciencia e a Tecnologia (FCT/MCTES) in Portugal for her assistant researcher contract under the Scientific Employment Stimulus (2020.01555.CEECIND). The Associate Laboratory for Green Chemistry - LAQV also acknowledges the financial support from FCT/MCTES (UIDB/50006/2020 and UIDP/50006/2020)