Thermal and Structural Study of the Crystal Phases and Mesophases in the Lithium and Thallium(I) Propanoates and Pentanoates Binary Systems: Formation of Mixed Salts and Stabilization of the Ionic Liquid Crystal Phase

• Published in: The journal of physical chemistry. B 2010-08, Vol.114 (31), p.10075-10085
• Main Authors: Martínez Casado, F. J, Ramos Riesco, M, da Silva, I, Labrador, A, Redondo, M. I, García Pérez, M. V, López-Andrés, S, Rodríguez Cheda, J. A
• Format: Article
• Language: English
• Subjects: B: Surfactants, Membranes
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp1031702

The temperature and enthalpy vs composition phase diagrams of the binary systems [xC2H5CO2Li + (1 − x)C2H5CO2Tl], and [x(n-C4H9CO2Li) + (1 − x)n-C4H9CO2Tl], where x is the mole fraction, were determined by DSC. Both binary systems display the formation of one 2:1 mixed salt each (at x = 0.667) that appear as a peritectic (incongruent melting) at T fus = 512.0 K, and T fus = 461.1 K, with Δfus H m = 13.76 and 8.08 kJ·mol−1 for Li−Tl (I) propanoates, and n-pentanoate mixed salts, respectively. The thermotropic liquid crystal of the thallium(I) n-pentanoate transforms into a more stable liquid-crystal phase, which appears in the phase diagram between 380 and 488 K and for x = 0 up to x = 0.56. The crystal structure of thallium(I) propanoate and of the two mixed salts were obtained via X-ray synchrotron radiation diffraction measurements. These compounds present a bilayered structure similar to the two pure lithium salts previously found by our group.