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

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 (C(n)mimPF(6), 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 C(n)mimPF(6) 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 C(n)mimPF(6), 4.5 wt% C(n)mimPF(6)/LLCs can reduce the friction and wear of sliding pairs. The better lubricating property and antiwear capability of the C(n)mimPF(6)/LLCs may be attributed to the increasing of the interlayer thickness d and the decreasing of the bilayer thickness d(0) in microstructures. This work provides a better understanding of the relationship between the microstructures and friction wear performances of ILs/LLCs. (C) 2018 Published by Elsevier Inc.