Thermal conductivity of betaine-glycerol, betaine-1,2-propanediol based deep eutectic solvents

• Nine betaine based deep eutectic solvents (DESs) have been synthesized. • Thermal conductivity of these DESs are reported for the first time. • The thermal conductivity linearly increases with the temperature rise. As the analog of ionic liquids, deep eutectic solvents (DESs) have drawn intense attention and are considered as a novel class of green solvents. Due to their splendid advantages such as low melting points, low vapor pressure, high thermal stability, wide liquid ranges and low price. DESs have been researched for a wide range utilization in many areas. Especially they have been investigated as heat transfer fluids recently. Thermal conductivity is an important transport property that influences the convective heat transfer. Nonetheless, very limited data is available on the thermal conductivity of DESs. In this work, nine DESs were prepared by using betaine as hydrogen bond acceptor and glycerol or 1,2-propanediol as hydrogen bond donor. Then, the thermal conductivities of these DESs were measured in a large temperature range (293 to 373 K) at atmospheric pressure. The thermal conductivity measurement had a combined expanded uncertainty better than ± 2.0% (in the 0.95 confidence level).