Abstract
Ionic liquids (ILs) have a wide variety of applications in modern electrochemistry due to their unique electrolytic properties. In particular, they are promising candidates as dopants for polymeric membranes in potentiometric sensors and liquid-junction free reference electrodes. However, the effective use of ILs requires a comprehensive understanding of their electrolytic behavior in the polymeric phase. We report here the exploration of the electrolytic and diffusion properties of IL 1-hexyl-3-methyl-1H-imidazol-3-ium bis[(trifluoromethyl)sulfonyl]amide ([C6Meim][NTf2]) in a poly(vinyl chloride) matrix. Chronopotentiometry is utilized to determine the concentration of charge carriers, ionic diffusion coefficients and apparent dissociation constant of [C6Meim][NTf2] in PVC membranes plasticized with a mixture of [C6Meim][NTf2] and bis(2-ethylhexyl) sebacate (DOS) over a wide range of IL concentrations. The diffusion properties of [C6Meim][NTf2] are confirmed by NMR-diffusometry. The non-monotonic electrolytic behavior of the IL in PVC-DOS matrix is described for the first time. A maximum ionization degree and diffusion coefficient is observed at 30 wt.% of IL in the plasticizing mixture. Thus, it is shown that by varying the flexible parameter of the IL to plasticizer ratio in the polymeric phase one can tune the electrolytic and transport properties of sensing PVC membranes.
Highlights
Publisher’s Note: MDPI stays neutralIonic liquids (ILs) are increasingly used in various fields of science
poly(vinyl chloride) (PVC) membranes doped with mixtures of bis(2-ethylhexyl) sebacate and IL 1-hexyl-3-methyl-1H-imidazol-3-ium bis[(trifluoromethyl)sulfonyl]amide were studied by means of chronopotentiometry and NMR-diffusometry
The values of ionic diffusion coefficients were verified and the diffusion coefficient for the ion pair [C6 Meim]+ [NTf2 ]− was evaluated with the PFG-NMR technique
Summary
Publisher’s Note: MDPI stays neutralIonic liquids (ILs) are increasingly used in various fields of science. High ionic conductivity, non-volatility, relatively low toxicity, a large electrochemical window and good electrochemical stability make ILs promising organic solvents for studying electrochemical processes and for use in a number of analytical methods (electrochemical [1], chromatographic [2,3], etc.). The use of ILs in the polymeric membranes of both potentiometric [7,8] and optical [9,10,11] sensors has been the focus of the chemical sensor community over the past decade, mainly due to their multifunctional performance. ILs can serve as active sensor components (ionophores and/or ionic additives) [8,12,13], at the same time plasticizing the polymeric sensing phase [7,14,15]. High stability and reproducibility of electrochemical sensor characteristics was achieved in [15] by using asymmetric imidazolium-based
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