Protic ionic liquids (PILs) are a subset of ionic liquids formed by the equimolar mixing of a Brønsted acid and a Brønsted base. PILs have been categorized as poor ionic liquids. However, the issue of assessing the ionicity of PILs is still a matter of debate. In this work we studied some physicochemical properties of three chosen PILs, namely, ethanolammonium acetate (EOAA), 2-methylbutylammonium formate (2MBAF), and pentylammonium formate (PeAF), at the initial equimolar (stoichiometric) acid/base ratio and in the presence of excess acid and base. DSC phase-transition studies along with NMR, IR, and Raman spectroscopy were performed on the chosen PILs. The results are discussed in terms of the degree of ionization (extent of proton transfer from the Brønsted acid to Brønsted base), and the possibility of the formation of polar 1:1 complexes and larger aggregates in the neat stoichiometric PILs.

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The angular, temperature, and frequency dependences of the proton spin-lattice relaxation rate Til in the smectic A phase of TBBA have been determined. An analysis is made of the possible relaxation mechanisms in smectic A systems. The results seem to show that the angular dependence of Til is produced by the modulation of the intramolecular dipolar interactions dUe to the coupling between selfdiffusion and local "director" fluctuations. The low temperature smectic phases of TBBA have been as well investigated. The decrease in the self-diffusion constant due to two-dimensional translational ordering at the smectic C--+smectic H transition is shown to produce a dramatic increase in Tl and decrease in TID' The rotation of the chain segments abruptly slows down on going from smectic H to smectic VI and discontinuously freezes out on going from smectic VI to smectic VII.

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