Lyotropic La-containing lamellar liquid crystals: phase behaviour, thermal and structural properties

Abstract

This paper provides the results of POM, DSC and XRPD methods characterizing the liquid crystalline behaviour, thermal properties and structural parameters of lyotropic systems based on a nonionic surfactant and lanthanum nitrate (La³⁺). The systems based on tetraethylene glycol monododecyl ether (C₁₂EO₄) and lanthanum nitrate have been demonstrated to form a lamellar phase. The concentration and temperature ranges of the existence of mesophases as well as thermodynamic parameters of phase transitions have been estimated. The structural parameters of the lamellar phase of the C₁₂EO₄/La³⁺/water systems have been determined using X-ray diffraction. The model of molecular packing in lamellar lanthanide-containing lyotropic mesophases was proposed for the observed patterns of structural parameters obtained at various water contents. NMR ¹H with a pulsed magnetic field gradient has been used to characterize molecular motions in the C₁₂EO₄/La³⁺/H₂O systems with different water contents.