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Picolinium‐Based Hydrophobic Ionic Liquids as Additives to PEG200 to Lubricate Steel‐Silicon Contacts
Author(s) -
Donato Mariana T.,
Caetano Fernando,
Colaço Rogério,
Branco Luís C.,
Saramago Benilde
Publication year - 2020
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.202000613
Subject(s) - ionic liquid , materials science , trifluoromethanesulfonate , lubrication , silicon , chemical engineering , tribology , surface roughness , polyethylene glycol , ion , polymer chemistry , composite material , organic chemistry , catalysis , metallurgy , chemistry , engineering
Three new ionic liquids (ILs) containing the picolinium cation were synthesized using a more sustainable method based on microwave (MW) irradiation: 1‐hexyl‐2, 3 or 4‐picolinium trifluoromethanesulfonate ([C 6 ‐x‐pic][TfO] where x=2, 3 and 4. The objective was, besides testing MW reactions with higher yields and lower reaction times comparing to conventional heating process, to assess the tribological behavior of these ILs as additives to base oil polyethylene glycol (PEG200). The friction coefficients (CoFs) for the pair silicon surface/steel sphere were compared to those obtained with other ILs based on the same anion. The ILs with cations containing one hexyl or butyl side chain led to lower CoFs, and [C 6 ‐4‐pic][TfO] was the most efficient additive, which may be attributed to the cation symmetry. The roughness of the sliding surfaces was reduced after the tribological test using neat PEG200, but, when the additive [C 6 ‐4‐pic][TfO] was added, the roughness was practically not affected. It seems that [C 6 ‐4‐pic][TfO] adsorbs forming ordered layers that support the load together with the liquid film retained among the asperities of the opposing surfaces.