Toward understanding the requirements for synthesizing organized organic-inorganic biomimetic microstructures.

摘要

The literature about the structure and formation mechanisms of seashell nacre was examined for clues as to principles that could be used to synthesize a material with an organized organic-inorganic microstructure. An overall theme was found to be the importance of an organic phase, possibly preorganized, in influencing and controlling the shape, phase, and orientation of inorganic crystals. Current published biomimetic strategies were also reviewed.; In this work, several approaches at synthesizing an organized material were taken. Preliminary investigations centered around the topic of inorganic crystal precipitation in the presence of organic molecules. The first set of experiments studied the effect of soluble organic molecules such as polymers and citric acid on calcium sulfate shape formation. In order to make a 3-dimensional material, self-organizing organic systems were investigated. A hydrophobic monomer (MMA) was mixed with a surfactant (DDAB) and an aqueous solution of calcium sulfate into the cubic phase. The MMA was polymerized to PMMA, and the calcium sulfate crystals were allowed to precipitate. An interesting lamellar PMMA microstructure resulted, with limited areas in which the calcium sulfate precipitates were aligned.; Focus then shifted to the role of inorganic additives, supersaturation, and inorganic substrates on crystal shapes and organization. First, experimental design techniques were used to study the influence of combinations of variables on shape formation in both the calcium sulfate and calcium carbonate systems. A unique calcite sphere morphology was found when Mg{dollar}sp{lcub}2+{rcub}{dollar} was combined with SO{dollar}sb4sp{lcub}2-{rcub}{dollar} in the solution during precipitation.; Next, a new procedure was developed to form 2-dimensional materials at air-limewater interfaces. The effect of additives and Langmuir monolayers on shape formation was studied, as well as methods to grow 3-dimensional materials from solutions using multilayering techniques.; Finally, the ability of calcium carbonate crystals to align on inorganic substrates was discovered. The effect of changes in various conditions such as atmosphere, presence of water, and substrate composition were described. The organization of these structures prompted new strategies for synthesizing lamellar eutectics of organic and inorganic materials.