Reversible phase transformation gel-type ionic liquid compounds based on tungstovanadosilicates

Abstract A series of new reversible phase transformation gel-type ionic liquid compounds, [PyPS] 5 SiW 11 VO 40 , [PyPS] 7 SiW 9 V 3 O 40 , [TEAPS] 5 SiW 11 VO 40 and [TEAPS] 7 SiW 9 V 3 O 40 , have been synthesized from two organic ammoniums 1-(3-sulfonic group) propyl-pyridine (PyPS), 1-(3-sulfonic group) propyl-triethylammonium (TEAPS) and vanadium-substituted heteropoly acids H 5 SiW 11 VO 40 and H 7 SiW 9 V 3 O 40 . The products can undergo a phase transformation from viscous gel-state to liquid-state below 100 °C, and ionic conductivity up to 10 −3  S cm −1 was observed at 110 °C for these gel-type POM-ILs. The relationship between the component elements of the products and their physicochemical property has been studied. Their thermostability was measured using thermogravimetric and differential thermal analysis (TG-DTA), and the result indicates that the less vanadium atoms there are inside the heteropoly anion, the more stable the POM-IL is at high temperature. Cyclic voltammetry is carried out to study their electrochemical properties in organic solution. The potential values of redox waves confirm that the oxidability of these gel-type POM-ILs can be controlled upon changing the number of vanadium atoms in the heteropolyanions.