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In Situ Investigation of Complex BaSO4 Fiber Generation in the Presence of Sodium Polyacrylate. 1. Kinetics and Solution Analysis

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posted on 10.10.2006, 00:00 by Tongxin Wang, Helmut Cölfen
Simple solution analysis of the formation mechanism of complex BaSO4 fiber bundles in the presence of polyacrylate sodium salt, via a bioinspired approach, is reported. Titration of the polyacrylate solution with Ba2+ revealed complex formation and the optimum ratio of Ba2+ to polyacrylate for a slow polymer-controlled mineralization process. This is a much simpler and faster method to determine the appropriate additive/mineral concentration pairs as opposed to more common crystallization experiments in which the additive/mineral concentration is varied. Time-dependent pH measurements were carried out to determine the concentration of solution species from which BaSO4 supersaturation throughout the fiber formation process can be calculated and the second-order kinetics of the Ba2+ concentration in solution can be identified. Conductivity measurements, pH measurements, and analytical ultracentrifugation revealed the first formed species to be Ba−polyacrylate complexes. A combination of the solution analysis results and optical microscopic images allows a detailed picture of the complex precipitation and self-organization process, a particle-mediated process involving mesoscopic transformations, to be revealed.