ionic liquid lubricants show excellent anti-friction and wear-resistant properties either as lubricating base oil or as lubricant additives. However, the synthesis of ionic liquid lubricants is complicated and costs much.

To solve the problem, researchers from the State Key Laboratory of Solid Lubrication at the Lanzhou Institute of Chemical Physics of the Chinese Academy of Sciences (CAS) have, for the first time, introduced the concept of in-situ preparation of ionic liquid as lubricant additives into the synthesis of lubricants.

They have incorporated metal salt or the combination of metal salt and functional organic molecule into the base oil. With the formation of charge-transfer complex between salt and base oil molecule or between salt and functional organic molecule, coordinated ionic liquids are in-situ prepared as the lubricant additives in base oil.

It is found that the miscibility of these ILs with the base oil is better than conventional imidazolium ILs and other unfunctionalized lithium-based ILs. The corrosion test reveals that the synthetic ILs have superior anti-corrosion properties than the conventional IL, L-B104, due to the presence of function organic groups. They also showed excellent tribological performances that were superior to the commonly used additive T204.

This method opens up the possibility of preparing new functionalized IL lubricant additives in situ in base oils.

The work has received support from the National Natural Science Foundation of China and the Ministry of Science and Technology of China.

The above work has been published in several journals and five Chinese invention patents have been applied concerning the findings.

  

Scheme of the in-situ preparation of ionic liquid as lubricant additives (Image by LIU Weimin et al.)

 

In-situ preparation of IL additives in polyether oil and study of their tribological properties (Image by LIU Weimin et al.)

 

In-situ preparation of IL additives in synthetic ester oil and study of their tribological properties (Image by LIU Weimin et al.)

List of publications

1. Fan, M. -J.; Liang, Y. -M; Zhou, F.*; Liu, W. -M.* Dramatically Improved Friction Reduction and Wear Resistance by in situ Formed Ionic Liquids. RSC Adv. 2012, 2, 6824-6830. (http://pubs.rsc.org/en/content/articlehtml/2012/ra/c2ra20888a) 

2. Fan, M. -J.; Song, Z. -J, Liang, Y. -M; Zhou, F.*; Liu, W. -M.*  In situ Formed Ionic Liquids in Synthetic Esters for Significantly Improved Lubrication. ACS Appl. Mater. Interfaces, 2012, 4, 6683-6689. (http://pubs.acs.org/doi/abs/10.1021/am3018042) 

3. Song, Z. H.; Fan, M. -J.; Liang, Y. -M.*; Zhou, F.*; Liu W. -M.* Lithium Based Ionic Liquids: in situ Formed Lubricant Additive Only by Blending. Tribol. Lett. 2013, 49, 127–133. (http://link.springer.com/article/10.1007%2Fs11249-012-0046-1#) 

4. Song, Z. H.; Liang, Y. -M.; Fan, M. -J.; Zhou, F.; Liu W. -M.* Lithium-based Ionic Liquids as Novel Lubricant Additives for Multiply Alkylated Cyclopentanes (MACs). Friction, 2013, 1, 222231. (http://link.springer.com/article/10.1007%2Fs40544-013-0019-x#) 

5. Song, Z. H.; Cai, M. R.; Liang, Y. -M.; Fan, M. -J.*; Zhou, F.; Liu W. -M.* In situ Preparation of Anti-corrosion Ionic Liquids as the Lubricant Additives in Multiply-Alkylated Cyclopentanes. RSC Adv. 2013, 3, 21715-21721. (http://pubs.rsc.org/en/content/articlelanding/2013/ra/c3ra42092b#!divAbstract) 

6. Song, Z. H.; Liang, Y. -M.; Fan, M. -J.; Zhou, F.; Liu W. -M.* Lithium-based Ionic Liquids Functionalized by Sym-triazine and Cyclotriphosphazene as High Temperature Lubricants. Tribol. Inter. 2014, 70, 136-141. (http://www.sciencedirect.com/science/article/pii/S0301679X13003356)