ISSN 1023-1935, Russian Journal of Electrochemistry, 2013, Vol. 49, No. 8, pp. 801–806. © Pleiades Publishing, Ltd., 2013. Original Russian Text © L.V. Shmygleva, A.V. Pisareva, R.V. Pisarev, A.E. Ukshe, Yu.A. Dobrovol’skii, 2013, published in Elektrokhimiya, 2013, Vol. 49, No. 8, pp. 893–898. 801 INTRODUCTION The search for new solid electrolytes with high pro- ton conductivity at low temperatures is actively carried out all over the world; a lot of publications are devoted to this subject. Of special importance is the develop- ment of polymer membranes with efficient proton transport. This is associated with the possibility of practical application of such materials in electro- chemical devices of various types [1, 2]. Much fewer publications were devoted to low-molecular proton conductors including crystalline conductors. At the same time, it is important to study the rela- tionship between the structure of low-molecular superprotonics and their transport properties in order to understand the mechanism of ion transfer in solids and use such materials in various solid-state electro- chemical devices (sensors, fuel cells, etc.) [3, 4]. Among these proton conductors, a whole class of compounds containing group, namely, sulfonic acids, can be singled out. In our earlier studies we have shown that the conductivity of hydrates of various benze- nesulfonic acids [5–8] can reach 10 –3 –10 –4 S cm –1 with the increase in the environmental humidity. At the same time, the conductivity of sulfonated fullerenoles in dry atmosphere reaches 10 –3 S cm –1 [9–11]. However, there is another class of compounds, namely, calixarenes with the layered structure in which rigid fragments of the organic network are intercepted by layers formed by proton-generating groups sur- rounded by considerable amount of crystallization water [12]. Recently, we have shown [13] that in such compounds, ion transfer can occur to produce com- SO 3 – pounds with record-breaking proton conductivity. The goal of this study is to investigate the transport proper- ties of calixarenes as a function of the nature of substit- uents. EXPERIMENTAL The proton conductivity of the following two calyx[4]arene-para-sulfonic acids is studied: 5,11,17, 23-tetra-sulfo-25,26,27,28-tetra-hydroxycalix[4]arene (I), and 5,11,17,23-tetra-sulfo-25,26,27,28-tetrakis- (ethoxycarbonylmethoxy)-calix[4]arene (II), which were synthesized by sulfonation of the original calyx[4]arene [14, 15]. In their lattice, the individual molecules of these compounds are packed in the stag- gered order into the layers (Fig. 1b) with sulfo groups oriented outside. Due to the presence of a long chain at the benzene ring in compound (II), the distance between molecules in such layer should be longer; hence, the extra water molecules are required at each sulfo group in order to form a continuous bridge (Fig. 1). Thus a possibility arises to study the effect of the distance between molecules in this layer on the transport properties of these compounds. The thermal stability of samples was determined by the synchronous thermal analysis (STA) combined with the mass spectrometric analysis of decomposition products on instruments manufactured by Netzsch STA 409 PC Luxx  and QMS 403 C Aëolos. TG and DTA curves were recorded in the temperature range of 298–773 K in argon at the heating rate of 10 K/min. The proton-transfer parameters for powder sam- ples were determined by impedance spectroscopy in the temperature range of 293–323 K. In the measure- ments, we used symmetrical cells: C/studied electro- lyte/C (C is the carbon foil) pressed under pressure of 10 MPa and kept in the environment of fixed humidity. The establishment of equilibrium with the environ- Proton Conductivity of Calix[4]arene-para-sulfonic Acids 1 L. V. Shmygleva z , A. V. Pisareva, R. V. Pisarev, A. E. Ukshe, and Yu. A. Dobrovol’skii Institute of Problems of Chemical Physics, Russian Academy of Sciences, pros. Akademika Semenova 1, Chernogolovka, Moscow oblast’, 142432 Russia Received October 19, 2012 Abstract—The proton conductivity of hydrates of calix[4]arene-para-sulfonic acids is studied. The high pro- ton conductivity is observed at ambient temperatures in the wide ranges of environmental humidity and, cor- respondingly, water content in the hydrate. For the air humidity of 10 rel. %, the conductivity of compounds is 10 –4 –10 –3 S cm –1 and approaches 10 –2 –10 –1 S cm –1 as the humidity increases up to 70 rel. %. Keywords: calix[4]arene-para-sulfonic acids, proton conductivity, activation energy DOI: 10.1134/S1023193513080181 1 This publication was prepared on the basis of a report delivered at the XI Meeting “Fundamental Problems of Solid State Ion- ics”, Chernogolovka, 2012. z Corresponding author: shmygleval@mail.ru (L.V. Shmygleva).