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

Abstract

The zinc nitrate salt acts as a solvent in the ZnX-C 12 EO 10 (ZnX is [Zn(H 2 O) 6 ](NO 3 ) 2 and C 12 EO 10 is C 12 H 25 -(OCH 2 CH 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 þ 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.

Molten‐Salt‐Assisted Self‐Assembly (MASA)‐Synthesis of Mesoporous Metal Titanate‐Titania, Metal Sulfide‐Titania, and Metal Selenide‐Titania Thin Films

“…This is a well-known physicochemical behavior of solutions (known as colligative properties and depression of the melting point of solvents in the presence of impurities). Therefore similar physicochemical phenomena are happening in a confi ned space at much lower temperatures [ 10 ] in the hydrophilic domains of the mesophases. Otherwise, it is impossible to keep the salt species in the mesostructures at such high concentrations (higher than the solubility limit of the salts in water).…”

“…[ 9 ] We recently found that salt-surfactant LLC self-assembly occurs because the salt melts and acts as a solvent in the assembly process. [ 10 ] Note also that in a confi ned space (the hydrophilic domains of the mesophase), the melting point of the salt drops drastically and the molten salt never crystallize even down to liquid nitrogen temperatures due to the soft confi nement effect (SCE). [ 10 ] The addition of a charged surfactant to the salt-oligo(ethylene oxide) non-ionic surfactant LLC phase further increases the amount of salt in the LLC mesophase.…”

“…[ 10 ] Note also that in a confi ned space (the hydrophilic domains of the mesophase), the melting point of the salt drops drastically and the molten salt never crystallize even down to liquid nitrogen temperatures due to the soft confi nement effect (SCE). [ 10 ] The addition of a charged surfactant to the salt-oligo(ethylene oxide) non-ionic surfactant LLC phase further increases the amount of salt in the LLC mesophase. [ 11 ] Collaborative assembly of these two surfactants and the interaction of the charged hydrophilic-hydrophobic interface of the surfactant domains in the LLC mesophase, with the molten salt domains further stabilize the salt-surfactant LLC mesophases.…”

Synthesis of manganese oxide supported on mesoporous titanium oxide: Influence of the block copolymer

“…Our attention focuses on the influence on the material structure of (i) the presence of the block copolymer and (ii) the nature of the manganese salt used as the precursor. Block copolymers have been shown to form complexes with metal cations [54][55][56]. Manganese oxide could be introduced either inside the titania walls or at the titania surface by choosing a good manganese precursor having more or less affinity either with the polymer and/or with the titania sol.…”

Molten Salt Assisted Self Assembly (MASA): Synthesis of Mesoporous Metal Titanate (CoTiO3, MnTiO3, and Li4Ti5O12) Thin Films and Monoliths

“…1 Organizing surfactants into lyotropic liquid crystalline (LLC) mesophases by using molten salts can be beneficial in the production of new materials for clean energy applications. 2,3 Recently, we have demonstrated that the molten phase of salts can be used as a solvent in the synthesis of mesoporus metal oxide modified silica 2 as well as titania.…”