The Biomimetic Mineralization Of Calcium Carbonate In The Micellar And Lyotropic Liquid Crystal System Formed By Metal Dodecyl Sulfates

The biomineralization materials with unique structures and properties have attracted scientists much attention over the last 20 years, the control of the formation of biominerals shows a new way for the fabrication of functional organic/inorganic materials under the mild condition. In this thesis, the crystallization habit of calcium carbonate was investigated in the presence of dodecyl sulfate anions.When definite amount of sodium dodecyl sulfate (SDS) was dissolved in a polar solvent, micelles formed, which could self-organized to construct the complex architecture of hexagonal lyotropic liquid crystals. The liquid crystal possessing hydrophobic domains composed of surfactant hydrocarbon chains and hydrophilic regions between polar head-groups. The hexagonal lyotropic liquid crystal could exert a template effect on the formation of inorganic particles. In the hydrophilic regions of templates, calcium carbonate particles were confined. Transmission electron microscopy (TEM) results also proved that the unstable amorphous calcium carbonate could be stabilized for a long time. The addition of n-pentanol could also induce the crystallization of SDS, which will be our next conduction.Then the functional surfactant, calcium dodecyl sulfate (CDS), was introduced and used for the first time both as an anionic surfactant and as the source of mineral ions in the precipitation process of calcium carbonate. Concentration variations of CDS and/or n-pentanol in aqueous systems could lead to the formation of different self-assembled structures, i.e., the micellar, the lamellar lyotropic liquid crystal, and so on.The bound calcium ions on the surface of CDS self-assemblies simulate, more or less, the selective enrichment and/or extraction of mineral elements in biomineralization. Through the fine tuning of the ratio between water and alcohol can adjusted interaction between the polar groups and polar groups, polar groups and calcium ions. The simple reaction of the enriched Ca²⁺ ions at the so-called organic/inorganic interfaces with the slowly bubbled CO₂ gas resulted in the metastable vaterite polymorph with various structures. The single-crystalline vaterite of the hexagonal platelets, the lens-shaped structures with hexagonal symmetry, the olive-shaped superstructures and these with a concave at each top of olives were obtained, respectively, depending upon the concentration ratio between CDS and n-pentanol. The synergistic effect of CDS and n-pentanol was supposed to play a crucial role in driving the oriented aggregation of metastable nanoparticles. Simultaneously, the novel phase transformation of vaterite to aragonite was observed, implying the possible formation mechanism of aragonite at room temperature and in the absence of magnesium ions.Calcium dodecyl sulfate(CDS) can solved in the mixed solution of n-pentanol and ammonia, then formed lamellar lyotropic liquid crystals. The lyotropic liquid crystals were used to synthesized calcium carbonate, The rhombohedron, the hexagonal platelets, and the firewood-buddle like particles of calcium carbonate, which composed of hexagonal prism, were obtained. The template effects of the lamellar lyotropic liquid crystals, and the formation mechanisms of incomplete hexagonal platelets and firewood-buddle like calcium carbonate particles, were discussed.