Release of a model molecule from highly concentrated fluorinated reverse emulsions. Influence of composition variables and temperature.

Highly concentrated reverse emulsions have been used to study the diffusion of a model molecule entrapped in these gel-emulsions. The influence of several parameters on the release of coumarin from fluorinated gel-emulsions has been investigated, and a computational method has been elaborated to determine the numerical value of the diffusion coefficients. The amount of probe molecule released depends on the initial loading amount, whereas the diffusion coefficient is not influenced by the initial concentration or by the amount of surfactant in the emulsions (in the range of the oil-to-surfactant ratios studied). The predominant factor seems to be the amount of water permitting the increase of the inter-phase area. Moreover, we have shown that the release of coumarin from gel-emulsions is in accord with the 'Arrhenius' law and the 'activation energy' deduced can be due to a barrier counteracting the diffusion.