Novel Method for Calculating the Diffusion Coefficients of a Ternary System Containing a Polydisperse Component. Applications to the Gouy Interferometry

• Published in: The journal of physical chemistry. B 2003-07, Vol.107 (29), p.7216-7224
• Main Authors: Mangiapia, Gaetano, Paduano, Luigi, Vergara, Alessandro, Sartorio, Roberto
• Format: Article
• Language: English
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp027435o

The common approach of neglecting the effect of polydispersity on matter transport leads, in multicomponent systems, to thermodynamic inconsistency at infinite dilution of all of the solutes. Furthermore such an approximation could cause an incorrect determination of the diffusion coefficients if the standard calculation procedures are applied. We present a novel approach to correct for the effect of the polydispersity of a solute on the values of the basic Gouy parameters D A “the reduced height-area ratio” and Q 0 “the area under the Ω graph” used in the Fujita-Gosting procedure to compute the four diffusion coefficients of a ternary system containing a polydisperse component. The proposed procedure satisfies the thermodynamic requirements at infinite solute dilution. To verify the reliability of our method, a series of simulations on the ternary aqueous system containing poly(ethyleneglicol) 200 and poly(ethyleneglicol) 400 in the presence of a monodisperse solute have been performed. For the polymeric sample, Poisson and Zimm−Schultz distributions have been considered. In both cases, our procedure has been applied successfully up to dilute concentration of components present in the system.