title: In situ investigation of complex BaSO4 fiber generation in the presence of sodium polyacrylate. 1. Kinetics and solution analysis.
abstract: Simple solution analysis of the formation mechanism of complex BaSO(4) fiber bundles in the presence of polyacrylate sodium salt, via a bioinspired approach, is reported. Titration of the polyacrylate solution with Ba(2+) revealed complex formation and the optimum ratio of Ba(2+) 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 BaSO(4) supersaturation throughout the fiber formation process can be calculated and the second-order kinetics of the Ba(2+) 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.
authors.affiliation: Max-Planck Institute of Colloids and Interfaces, Colloid Chemistry, D-14424 Potsdam, Germany.
authors.forename: Tongxin
authors.initials: T
authors.lastname: Wang
authors.forename: Helmut
authors.initials: H
authors.lastname: Cölfen
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D001464:Barium / Q000737:chemistry; D001466:Barium Sulfate / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D012996:Solutions
chemical_list: D000180:Acrylic Resins; D002264:Carboxylic Acids; D007477:Ions; D012996:Solutions; D001464:Barium; D001466:Barium Sulfate; C006903:carbopol 940