Dynamic light scattering observation of droplet aggregation in a Winsor type W/O microemulsion system

Abstract

We have performed scattered light intensity autocorrelation measurements on a Winsor type microemulsion system composed of brine, cyclohexane, SDS and a mixture of 1-butanol and 1-pentanol. At high cosurfactant concentration, where the microemulsion phase was considered to consist of individual, spherical water-in-oil droplets of relatively low droplet volume fraction, the autocorrelation functions were observed to be essentially single exponential, as expected. Above a certain droplet volume fraction, however, additional decay modes were observed to enter the correlation data. These modes were interpreted to be due to rotation and/or internal motion of droplet aggregates.

Changes in Microemulsion and Protein Structure in IgG−AOT−Brine−Isooctane Systems

“…At a surfactant concentration of 0.4 M, on the other hand, the higher volume fraction of droplets is known to cause droplet-droplet attraction and clustering, even in the absence of protein. [36][37][38][39][40] These clusters may effectively shield the protein from aggregation or solvent-induced denaturation. As a result, in the presence of clusters more time is required for protein-protein collisions to lead to protein precipitation, and the formation of clusters can stabilize the protein (Figure 1b).…”

“…At an AOT concentration of 0.1 M, IgG in these individual drops is likely subjected to a destabilizing environment, such as exposure to the organic solvent or to other protein molecules due to droplet−droplet collisions. At a surfactant concentration of 0.4 M, on the other hand, the higher volume fraction of droplets is known to cause droplet−droplet attraction and clustering, even in the absence of protein. − These clusters may effectively shield the protein from aggregation or solvent-induced denaturation. As a result, in the presence of clusters more time is required for protein−protein collisions to lead to protein precipitation, and the formation of clusters can stabilize the protein (Figure b).…”

Time‐dependent solubilization of IgG in AOT‐brine‐isooctane microemulsions: Role of cluster formation

“…This decrease in relaxation rate suggests that IgG favors the formation of larger aggregates in the microemulsion, possibly containing clusters of w/o droplets. Cluster formation in w/o microemulsions has been observed by others as a result of substantial droplet±droplet attractive interactions, for example, at large droplet volume fractions in the absence of protein (Bellocq et al, 1980;Cebula et al, 1981;Majolino et al, 1989;Waaler et al, 1989;Kurumada et al, 1996). Large molecular weight neutral (Radiman et al, 1990;SchuÈ bel and Ilgenfritz, 1997;Laia et al, 2000) and amphiphilic (Hil®ker et al, 1991;Struis and Eicke, 1991;Fleischer et al, 1994) polymers are also thought to induce clustering.…”