Synthesis of dicationic symmetrical and asymmetrical ionic liquids and their tribological properties as ultrathin films

A new series of novel dicationic symmetrical and asymmetrical ionic liquids (ILs) consisting of tributylalkyl phosphonium and alkylimidazolium were synthesized. Their tribological properties in the form of spin-coated ultra-thin films sliding against AISI-52100 steel ball were studied in a ball-on-plate configuration on a Universal Micro-tribometer-2MT tester, using perfluoropolyether (PFPE) and normal ILs as comparisons. The best result is obtained for asymmetrical 1-(1-tributylphosphine-yl-hexyl)-3methylimidazolium dihexafluorophosphate, which has very high decomposition temperature-about 450 degrees C and good tribological properties.