Issue 47, 2009
From the journal:

Physical Chemistry Chemical Physics

Influence of flocculation and coalescence on the evolution of the average radius of an O/W emulsion. Is a linear slope of [R with combining macron]3vs. t an unmistakable signature of Ostwald ripening?

German Urbina-Villalba,*a   Ana Forgiarini,b   Kareem Rahna  and  Aileen Lozsána  

* Corresponding authors

a Instituto Venezolano de Investigaciones Científicas (IVIC), Lab. Fisicoquímica de Coloides, Centro de Física, Carretera Panamericana Km. 11, Aptdo. 20632, Caracas, Venezuela
E-mail: guv@ivic.ve
Fax: (58) 212-5041148

b Universidad de Los Andes, Lab. Formulación, Interfaces, Reología y Procesos (FIRP), Fac. de Ingeniería, Ave. Tulio Febres Cordero, Mérida 5101, Venezuela
E-mail: anafor@ula.ve
Fax: (58) 274-2402957

Abstract

The LSW theory of Ostwald ripening, predicts a linear variation of the cube of the average radius of a dispersion as a function of time ([R with combining macron]3vs. t) [I. M. Lifshitz, V. V. Slyozov, J. Phys. Chem. Solids, 1961, 19, 35–50; C. Wagner, Z. Elektrochem., 1961, 65, 581–591]. It also envisages a left-skewed drop-size distribution with a cut-off radius of 1.5[R with combining macron]. Consequently, non-linear changes of [R with combining macron]3vs. t are usually ascribed to either a transient period of time (previous to the attainment of the asymptotic limit of ripening) or other destabilisation processes. Up to now the effect of Brownian motion on Ostwald ripening (OR) has not been considered, although it is by far the strongest limitation of the LSW theory. In this work we show the results of incorporating the algorithm of De Smet et al. for Ostwald ripening simulations [Y. De Smet, L. Deriemaeker, R. Finsy, Langmuir, 1997, 13, 6884–6888] to our emulsion stability simulations (ESS) code. In particular, the short-time evolution of a dilute dodecane/water nanoemulsion in the absence of stabilisers is studied. At high ionic strength, the simulations suggest that [R with combining macron]3 can change linearly with time during the transient period of Ostwald ripening, due to the flocculation and the coalescence of the drops. This behavior is confirmed by the experiments for t < 100 s. At low ionic strength a concave downward curve is observed, both theoretically and experimentally.

Graphical abstract: Influence of flocculation and coalescence on the evolution of the average radius of an O/W emulsion. Is a linear slope of [[R with combining macron]] 3vs. t an unmistakable signature of Ostwald ripening?

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Article information

DOI
https://doi.org/10.1039/B915470A
Article type
Paper
Submitted
29 Jul 2009
Accepted
16 Sep 2009
First published
14 Oct 2009

Phys. Chem. Chem. Phys., 2009,11, 11184-11195

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Influence of flocculation and coalescence on the evolution of the average radius of an O/W emulsion. Is a linear slope of [R with combining macron]3vs. t an unmistakable signature of Ostwald ripening?

G. Urbina-Villalba, A. Forgiarini, K. Rahn and A. Lozsán, Phys. Chem. Chem. Phys., 2009, 11, 11184 DOI: 10.1039/B915470A

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