Studies On Ca²⁺,Mg²⁺-induced Vesicle Formation And Used As Templates

Above the critical micelle concentration (cmc) , surfactants can form various self-assembly aggregates, such as micelles, vesicles, micro-emulsions and liquid crystals etc. Vesicle phase, as one of them, has been a subject of fascinating research due to their potential applications in various fields such as colloid chemistry, bionics and material science. In recent years, three typical noncovalent interactions to form vesicles: hydrogen bonds, metal ion coordination and electrostatic attraction have been used as noncovalent attractive intermolecular interactions to control the self-assemblies of surfactants. Several surfactant systems in aqueous solutions are studied in this paper and the results are summarized as following:1 Ca²⁺/Mg²⁺-ligand coordinated vesicle phase was prepared in the mixed aqueous solution of tetradecyldimethylamine oxide (C₁₄DMAO) with calcium tetradecylamidomethylsulfate [(CH₃(CH₂)₁₃NHCOCH₂SO₄)₂Ca] and magnesium dodecylsulfate[Mg(DS)₂], respectively. At the right mixing ratios, Ca²⁺/Mg²⁺-ligand coordination results in the formation of molecular bilayers. The structures of the birefringent solutions were determined by transmission electron microscopy (TEM) images and rheological measurements, demonstrating the samples consist of vesicles.2 Ca²⁺-ligand complex vesicle phase was used as microreactors to prepare CaC₂O₄ crystals (Ca²⁺ + H₂C₂O₄→CaC₂O₄↓+ 2H⁺). Dimethyl oxalate as a precursor, which can hydrolyze to oxalic acid and ethanol. should precipitate Ca²⁺ ions coordinated in the bilayer films to produce CaC₂O₄ crystals. After removal of CaC₂O₄ particles, a new cationic/anionic (cataniomc) vesicle-phase solution was constructed from cationic C₁₄DMAOH⁺ (C₁₄DMAO + H⁺→C₁₄DMAOH⁺) and anionic CH₃(CH₁₂)₁₃NHCOCH₂SO₄^-. Magnesium oxide nanoplates was synthesized using ammonia hydroxide as precipitator in the presence of Mg²⁺-induced vesicle phase. The morphologies and structures of the synthesized crystals have been characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It is believed that the vesicle phase as microreactors play an important role in controlling the morphologies of crystals.