Pressurizing the mixtures of two ionic liquids: Crystallization versus vetrification. (20th September 2017)

• Record Type: Journal Article
• Authors: Capitani, F.; Trequattrini, F.; Palumbo, O.; Roy, P.; Postorino, P.; Paolone, A.
• Is Part Of: Journal of Raman spectroscopy. Volume 48:Number 12(2017)
• Page Start: 1819
• Page End: 1827
• Publication Date: 2017-09-20
• Subjects: high pressure -- Ionic liquids -- mixtures; Raman spectroscopy -- Periodicals; 535.846
• DOI: 10.1002/jrs.5257
• Languages: English
• ISSNs: 0377-0486

Abstract

Abstract: A series of mixtures prepared with different content of the ionic liquids N‐trimethyl‐N‐propylammonium bis(trifluoromethylsulfonyl)imide (TMPA‐TFSI) and N‐trimethyl‐N‐hexylammonium bis(trifluoromethylsulfonyl)imide (TMHA‐TFSI), namely, (TMPA‐TFSI)100− x (TMHA‐TFSI) x, is investigated by means of Raman spectroscopy as a function of pressure at room temperature. Both pure TMPA‐TFSI and the x = 2 mixture crystallize under an applied pressure lower than 1 GPa. On the contrary, for x > 7, none of the investigated mixtures crystallize, but they undergo a glass transition over the 1–2 GPa pressure range. We suggest that the disorder induced by the high number of possible configurations for the longer alkyl chain of TMHA‐TFSI in a compressed environment is a key factor in the suppression of the crystallization process. Abstract : Pure TMPA‐TFSI and the mixture (TMPA‐TFSI)100–x (TMHA‐TFSI)x with x =2 crystallize upon compression at a pressure below 1 GPa. The mixtures with x = 7, 15 and 50 do not crystallize, but rather transform into a glass state when a pressure between 1 and 2 GPa is applied. On increasing pressure, the concentration of the cis ‐TFSI increases, as it has a lower volume compared to trans ‐TFSI.