Origin of Lyotropic Liquid Crystalline Mesophase Formation and Liquid Crystalline to Mesostructured Solid Transformation in the Metal Nitrate Salt?Surfactant Systems

摘要

The zinc nitrate salt acts as a solvent in the ZnX?C_(12)EO_(10) (ZnX is [Zn(H_2O)_6](NO_3)_2 and C_(12)EO_(10) is C_(12)H_(25)(OCH_2CH_2)_(10)OH) lyotropic liquid crystalline (LLC) mesophase with a drastic dropping on the melting point of ZnX. The salt?surfactant LLC mesophase is stable down to ?52 °C and undergoes a phase change into a solid mesostructured salt upon cooling below ?52 °C; no phase separation is observed down to ?190 °C. The ZnX?C_(12)EO_(10) mesophase displays a usual phase behavior with an increasing concentration of the solvent (ZnX) in the media with an order of bicontinuous cubic(V_1)-2D hexagonal(H_1) ? a mixture of 2D hexagonal and micelle cubic(H_1 + I)?micelle cubic(I)?micelle(L_1) phases. The phase behaviors, specifically at low temperatures, and the first phase diagram of the ZnX?C_(12)EO_(10) system was investigated using polarized optical microscopy (POM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and Raman techniques and conductivity measurements.