Processes of mechanochemical degradation
of imidazolium bis((trifluoromethyl)sulfonyl)imide ionic liquids with
alkyl and monomethoxypoly(ethylene glycol) (mPEG) side groups were
studied using the novel technique of mechanically stimulated gas emission
spectroscopy. Mechanical stimulus caused degradation of both the anionic
and cationic moieties. For the latter, the degradation was concentrated
on the alkyl and ether chains rather than on the imidazole. For the
anionic moiety, various degradation steps associated with the emission
of CH
x
F
y
volatile
products followed by SO2 and SO3 emission were
identified. Simulation of frictional heat dissipation revealed that
tribochemical reactivity was induced by the mechanical energy supply
rather than the temperature increase. Thermal degradation of the same
ionic liquids studied using thermogravimetric analysis and Fourier transform infrared spectroscopy
was concentrated mainly on the cationic moiety. Thermal stability
significantly depended on the side chains. The decomposition of mPEG-functionalized
ionic liquids was a two-step process, where the lower temperature
step corresponded to mPEG decomposition.
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