Effect of Temperature and Water Content on the Properties of Solid Protic Electrolyte of Tetra Calixarene Sulfonic Acid: NMR Study

Abstract

The methods of ¹H NMR and pulsed field gradient NMR are used to study the protic solid electrolyte of calix[4]arene-para-sulfonic acid in the temperature range of –15 to 24°C and water content λ of 1.6 to 5.7 H₂O molecules per SO₃H. Analysis of the ¹H signal intensity in NMR spectra showed that no ice phase is formed in the whole studied temperature and water content range. The hydration numbers of H⁺(H₂O)_h complexes are calculated on the basis of the temperature dependences of chemical shift values. The pulsed field gradient NMR technique is used to determine self-diffusion coefficients. Activation energies E_act are calculated on the basis of the temperature dependences of self-diffusion coefficients. Good agreement of the data on diffusion E_act and protic conductivity are shown. A corollary of the Nernst–Einstein equation is used to calculate the values of protic conductivity on the basis of self-diffusion data. The calculated values of protic conductivity in the water content λ range of 1.6 to 5.7 agree with the data obtained experimentally.