Surfactant concentration effects continuous phase viscosity

In this process, one starts with the phase that should become the dispersed phase. We call this phase A. One then slowly adds the other phase (B) to phase A while the system is agitated (or rapidly flowing, or homogenized in a suitable machine). Initially, droplets of phase B are formed, which are broken up into small droplets by the agitation. In time, more and more of these droplets are formed However, one ultimately wants to have an emulsion of in 5 therefore, the surfactant system is dissolved in phase B and not in phase A. Thus, at a certain time, the emulsion becomes so concentrated and the viscosity becomes so high, that the droplets of B are sheared apart droplets of B then start to coalesce. As soon as this coalescence sets in, all droplets start to coalesce, as a snowball effect. So, suddenly the droplets of B combine and start to form a continuous phase, taking up droplets of phase A, which starts to be the dispersed phase. 

In these studies, polymeric nanocapsules with encapsulated dsDNA (790 base pairs) were produced via anionic polymerization of n-butylcyanoacrylate (BCA) carried out at the interface of homogeneously distributed aqueous droplets in inverse miniemulsion which are in a second step then redispersed in an aqueous continuous phase. The obtained capsules were characterized in terms of size, size distribution, morphology, polymer molecular weight, and encapsulation efficiency of DNA. The effects of surfactant type and concentration, viscosity of the continuous phase, monomer amount, and water-to-oil ratio were investigated and results are discussed in this paper. 

Effect of Surfactant Type, Concentration and Viscosity of the Continuous Phase... 

For surfactant concentrations close to or above the CMC, the Gibbs elasticity and the interfacial viscosity are large enough to immobilize the interface, = 0 (see Refs. 5, 58, 267, and 420). A similar effect is observed when the droplet dynamic viscosity is much larger than the dynamic viscosity of the continuous phase (e.g., in the bitumen emulsions, T d, is about 150,000 p at room temperature). For the case of fllm with inunobile surfaces, from Eq. (251) one can deduce the well-known Reynolds formula [466], in which the disjoining pressure, II, can be also included ... 

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