CNR ExploRA

Articolo in rivista, 2015, ENG, 10.1515/amm-2015-0064

Low Frequency Mechanical Spectroscopy Study of Three Pyrrolidinium Based Ionic Liquids

F. Trequattrini (1); A. Paolone (2); O. Palumbo (2); F.M. Vitucci (2); M.A. Navarra (3), S. Panero (3)

(1) Physics Department, Sapie4nza University of Rome, P.le A. Moro 5, 00185 Roma, Italy (2) CNR-ISC, U.O.S. La Sapienza, P.le A. Moro 5, 00185 Roma, Italy (3) Chemistry Department, Sapienza University of Rome, >P.lew A. Moro 5, 00185, Roma, Italy

In this work we present our recent results on three ionic liquids (ILs), which share bis(trifluoromethanesulfonyl) imide (TFSI) as anion and have different pyrrolidinium based cations. By means of a combination of mechanical spectroscopy and thermal analysis, many of the physical processes occurring during cooling down from the liquid phase, can be studied. Depending both on the diverse cation and the different thermal history, crystallization from the melt or glass transition, cold-crystallization, solid-solid phase transitions and thermally activated processes are observed. In one of the ILs, which could be easily undercooled, a prominent thermally activated peak could be observed above the glass transition. The temperature dependence of the relaxation time is approximated by a Vogel-Fulcher-Tamman equation, as usual for fragile glass forming liquids, and the apparent activation energy of W = 0.36 eV with a pre-exponential factor of the relaxation time tau(0) = 1.7.10(-13)s were derived supposing jumps between asymmetrical potential wells. The kinetics of the crystallization processes have been studied in the framework of the Johnson-Mehl-Avrami-Kolmogorov theory and the Avrami parameters have been derived for both the crystallization from the melt and for the cold crystallization observed on heating.

Archives of Metallurgy and Materials 60 (1), pp. 385–390