Properties and thermal behavior of natural deep eutectic solvents

Natural deep eutectic solvents (NADES) have shown to be promising sustainable media for a wide range of applications. Nonetheless, very limited data is available on the properties of these solvents. A more comprehensive body of data on NADES is required for a deeper understanding of these solvents at molecular level, which will undoubtedly foster the development of new applications. NADES based on choline chloride, organic acids, amino acids and sugars were prepared, and their density, thermal behavior, conductivity and polarity were assessed, for different NADES compositions. The NADES studied can be stable up to 170 Â°C, depending on their composition. The thermal characterization revealed that all the NADES are glass formers and some, after water removal, exhibit crystallinity. The morphological characterization of the crystallizable materials was performed using polarized optical microscopy which also provided evidence of homogeneity/phase separation. The conductivity of the NADES was also assessed from 0 to 40 Â°C. The more polar, organic acid-based NADES presented the highest conductivities. The conductivity dependence on temperature was well described by the Vogelâ Fulcherâ Tammann equation for some of the NADES studied.Fundação para a Ciência e a Tecnologia (FCT/MEC) through the grants PTDC/EQUEPR/12191/2010/ENIGMA, SFRH/BD/47088/2008 and SFRH / BPD / 44946 / 2008. We further acknowledge the financial support of FCT/MEC through the project ENIGMA — PTDC/EQU-EPR/121491/2010, and the project PEst-C/ EQB/LA0006/2013 and FCOMP-01-0124-FEDER-020646.We also acknowledge the funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement no. REGPOT-CT2012-316331-POLARIS, and from the Project “Novel smart and biomimetic materials for innovative regenerative medicine approaches (Ref.: RL1 — ABMR — NORTE-01-0124-FEDER- 000016)” co-financed by the North Portugal Regional Operational Programme (ON.2 — O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF)