Coaggregation of Two Anionic Azo Dyestuffs: A Combined Static Light Scattering and Small-Angle X-ray Scattering Study

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• 作者：Rolf Michels ; G眉nter Goerigk ; Ulla Vainio ; J茅r茅mie Gummel ; Klaus Huber
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：July 10, 2014
• 年：2014
• 卷：118
• 期：27
• 页码：7618-7629
• 全文大小：501K
• ISSN：1520-5207

文摘

The formation of azo dyestuff aggregates in dilute aqueous solution induced by the addition of Mg²⁺, Ca²⁺, Sr²⁺, or Ba²⁺ ions is followed by time-resolved static light scattering (SLS) and time-resolved small-angle X-ray scattering (SAXS). Time-dependent molar mass data of the growing aggregates is interpreted by means of a kinetic model introduced by Lomakin et al. ( Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 1125) for the description of 尾-amyloid aggregation. This interpretation reveals significant trends within the homologous series of alkaline earth cations. The trends refer to the nucleation and the growth rate of the dyestuff fibers. Time-resolved SAXS experiments indicate that these first two stages are followed by a third one during which a network forms by partial lateral alignment of fibers. At high enough dyestuff concentrations, this network formation even leads to a gel-like phase. Anomalous SAXS (ASAXS) on such a gel phase formed upon the addition of Sr²⁺ revealed the extent of neutralization of the dyestuff molecules within the gel by the specifically interacting alkaline earth cations.