Improvement in lubricating properties of TritonX-100/n-C10H21OH/H2O lamellar liquid crystals with the amphiphilic ionic liquid 1-alkyl-3-methylimidazolium hexafluorophosphate

Abstract

The applications of ionic liquids (ILs)/lamellar liquid crystals (LLCs) have great potential in nanotribology because they could be used where conventional oils could not work. To clarify the lubricating mechanism, herein, ILs/LLCs lubricants were prepared by addition of amphiphilic 1-alkyl-3-methylimidazolium hexafluorophosphate (CnmimPF6, n = 8, 12) into TritonX-100/n-C10H21OH/H2O LLCs with different concentration. The influence of alkyl chain lengths of ILs on the microstructures and the tribological properties of LLCs were investigated. The phase structure parameters and the tribological properties of the LLCs in the presence of CnmimPF6 were analyzed via freeze-fracture transmission electron microscopy (FF-TEM), the small-angle X-ray scattering (SAXS) technique, oscillating reciprocating friction and wear tester. Compared with the LLCs without CnmimPF6, 4.5 wt% CnmimPF6 /LLCs can reduce the friction and wear of sliding pairs. The better lubricating property and antiwear capability of the CnmimPF6/LLCs may be attributed to the increasing of the interlayer thickness d and the decreasing of the bilayer thickness d0 in microstructures. This work provides a better understanding of the relationship between the microstructures and friction wear performances of ILs/LLCs.