Lyotropic Liquid Crystalline Mesophases of Lithium Dihydrogen Phosphate and 10-Lauryl Ether Stabilized with Water or Phosphoric Acid

The molten phase of transition metal and lithium salts self-assemble with non-ionic surfactants to form lyotropic liquid crystalline (LLC) mesophases, which are important in the development of gel-electrolytes and mesoporous materials. Here, we show that LiH₂ PO₄ forms a semi-stable LLC mesophase with 10-lauryl ether (C₁₂ H₂₅ (OCH₂ CH₂ )₁₀ OH, C₁₂ E₁₀ ), decoded as Li-EO-X (X is LiH₂ PO₄ /C₁₂ E₁₀ mole ratio and between 2 and 200). The stability of the Li-EO-X phase is improved by increasing salt concentration (X>20) in the media. The semi-stable Li-EO-X mesophase is further stabilized by adding either water by controlling the humidity or H₃ PO₄ (PA) to the media. The phase behaviour of the above samples was investigated using POM, XRD, conductivity, and ATR-FTIR measurements. The addition of PA not only brings stability and higher conductivity (increase from 0.1 to 8.9 mS/cm) to the mesophase but also produce an LLC gel-electrolyte with a high buffer capacity that may be useful and important in various applications.