Thermal behaviour or thallium(I) fatty acid salts, I

Abstract

The electrical conductivity (EC) changes of thallium(I) salts of fatty acids, which possess liquid crystalline phases, were investigated as a function of temperature. It was found that sharp EC jumps are associated with the phase transitions. The EC of the liquid crystalline phases depended not only on the temperature, the molecular weight and the geometry of the measuring cell, but also very sensitively on the heat treatment conditions which affect the relative magnitude of the EC in the mesophases.Study of these dependences revealed a "memory effect". An explanation is given for this phenomenon.We have already reported on the thermodynamic data of the polymorphic and phase changes and on the characteristics of the thermal decompositions of the thallium(I) salts of fatty acids [1 ]. From the homologue having five carbon atoms, these salts possess thermotropic liquid crystalline phases, which belong to the amphiphile smectic type [2-4]. As a continuation of this work we have thoroughly investigated the thermoelectrical properties of these compounds, paying special attention to the behaviours of their mesophases. ExperimentalThe thallium(I) salts of saturated, open-chain, non-branching monocarboxylic acids (C1 -C9, Ca.o, C14, C16, and Cas ) were produced, purified and analysed in the previously-described way [1 ].Three different types of cells were applied for the measurement of electrical conductivity: a crucible type for the simultaneous DTA-TEC (differential thermoanalysis-thermal electrical conductivity) measurements, which was made of platinum [5,6], a glass capillary type [5,7,8], and a micro-cell with gold electrodes evaporated onto glass slide surfaces.

Theories and experimental investigations of the structural and thermotropic mesomorphic phase behaviors of metal carboxylates

“…For example, the phase sequence of thallium(I) hexanoate showed two first order transitions at ca. 204 and 208 K [139][140][141] in addition to several solid-solid phases and a single mesophase [142,143]. For the decanoate [144] four solid-solid transitions were observed at ca.…”

Ionic Liquid Crystals

“…320 Thallium(I) acetate, propionate, and butyrate salts are not liquid-crystalline, but all the other investigated homologues (up to thallium(I) behenate, C 21 H 23 COOTl) are. 320,321 The effect of chain branching on the thermal behavior has been investigated. 322 The thallium(I) salts of carboxylic acids with R-branching are not mesomorphic, whereas the salts of carboxylic acids with a branch in the -position exhibit a smectic mesophase.…”

Lithium–thallium(i) butyrates binary system: an intermediate salt and liquid crystal from non-mesogenic compounds.

“…Pure components. The thermal behavior of the two pure salts (LiC4 21,30 and TlC4 19,23 ) was studied previously, by adiabatic calorimetry and DSC. However, the results obtained in this work are in total agreement with the previous published results.…”

“…18 Pure lithium and thallium(I) butyrates have been studied separately by different calorimetric techniques, such as adiabatic calorimetry, 19,20 DSC, 21,22 and TG. 23,24 However, the crystal structure of alkanoates belonging to the respective series were solved in the last 2 years, for example LiC4, 25 LiC3 and LiC5, 26 anhydrous LiC2 and hydrates, 27 or TlC3. 18 Many binary phase diagrams have been analyzed 28 with the aim of finding new mesogenic phases or enlarging an existing thermotropic LC phase in the binary phase diagram.…”

“…[33][34][35] TlC4 was prepared by chemical reaction between the corresponding acid (butyric acid, Aldrich, ¢99%), and thallium(I) carbonate (Riedel-de Hae ¨n, ¢99%), in methanol (Merck, ¢99.8%). 19,23,4 The recrystallization was carried out for several times in an 1 : 1 ethanol/ether mixture (Merck, ¢99.8%, and Fluka, >99.8%, respectively), and vacuum dried. 18 The purity of the synthesized salts was assessed by differential scanning calorimetry (DSC), with values of 99.97, and 99.71%, for LiC4 and TlC4, respectively.…”