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On the physical significance of the adjusting parameters in the evaluation of the flocculation rate of an oil-in-water nanoemulsion

Abstract:

Recently a versatile methodology for the evaluation of the mixed flocculation-coalescence rate (kFC) of oil-in-water (o/w) nanoemulsions was proposed (Rahn-Chique et al., 2012c). The value of kFC is obtained fitting a theoretical expression of the turbidity of the emulsion (τteo) to its observed behavior (τexp) over a short period of time. The expression of τteo contains an additional parameter which was originally introduced to account for the fraction of collisions between the drops that lead to their aggregation (xa). Hence, under some approximations, the value of (1-xa) should represent the fraction of collisions that leads to the coalescence of the drops. Here, two sets of ionic nanoemulsions, and two sets of latex particles are used to study the dependence of xa with the average radius of the emulsion. The results suggest that despite its original justification, (1-xa) is more likely to represent the contribution of the 'spherical' scattering of light to the total optical cross section of the aggregates formed.