Time-Resolved Characterization of Dynamic Tribochemical Processes for Dicationic Imidazolium Ionic Liquid

Roman Nevshupa,Marcello Conte,Silvia Guerra,Elisa Roman

doi:10.3390/lubricants5030027

Abstract

Dynamic tribochemical processes for dicationic ionic liquid containing a geminal imidazolium cation head group bridged by a poly(ethylene glycol) and a bis(trifluoromethylsulfonyl)imide anion were studied using time-resolved mechanically stimulated gas emission mass-spectrometry (MSGE-MS). In comparison with similar monocationic imidazolium ionic liquids with short alkyl or long polyether side chains, the dicationic ionic liquid had a lower coefficient of friction on Ti6Al4V alloy and smoother behavior. The analysis of volatile decomposition products suggested multiple tribochemical reactions in which both anionic and cationic moieties are involved. The tribochemical degradation of cations was mainly through the detachment of the side and bridging chains from the imidazolium head groups. The absence of volatile products containing nitrogen implies that the imidazole group remained unchanged. Hydrogen and water desorption were attributed to the reactions of hydrogen fluoride being a product of anion degradation with titanium and titanium oxide, respectively.

Highlights

Room-temperature ionic liquids (ILs) are salt structures consisting of large cation and anion moieties, which are characterized by melting temperatures below 100 ◦ C
Dynamic tribochemical processes for dicationic ionic liquid containing a geminal imidazolium cation head group bridged by a poly(ethylene glycol) and a bis(trifluoromethylsulfonyl)imide anion were studied using time-resolved mechanically stimulated gas emission mass-spectrometry (MSGE-MS)
Stimulated gas emission spectrometry was applied for the study of dynamic Mechanically stimulated gas dicationic emission spectrometry was applied forcation the study of dynamic triboemission processes in geminal

Summary

Introduction

Room-temperature ionic liquids (ILs) are salt structures consisting of large cation and anion moieties, which are characterized by melting temperatures below 100 ◦ C. A new family of experimental techniques that combine tribometry with mass spectrometry or important information on the development of tribochemical processes in the course of a tribological surface sensitive techniques has recently emerged [48,49,50,51,52,53,54] In500 thebridging present work, probed tribochemical processes in dicationic ionic liquid usingwith mechanically stimulated gas emission (MSGE) This material was selected a PEG500 bridging chain and bis(trifluoromethylsulfonyl)imide (NTf2) anion on Ti6Al4V for the substrate because of the technological implications [26] and contrast theThis results of this substrate using mechanically stimulated gas emission (MSGE). Homologous monocationic ionic liquid [27,44]

Materials

Molecular structures

Experimental Techniques and Procedures

Results and Discussion

Conclusions