Emulsion micellar size effect

Therefore, the nonlinear relationship between rate of polymerization and the total surfactant concentration, as shown in Figure 2, was believed to be caused by a change in micellar size. Thus, the purpose of the present study was to verify the validity of the concept of micellar size effect in emulsion polymerization kinetics. Furthermore, although the Harkins-Smith-Ewart theory of micellar nucleation was proposed in 1948, and has found widespread application ever since, its validity is still challenged even for the case of polymerization of styrene ( ). If micellar... 

The basic concept of the present study was to show, other things being equal, that the rate of polymerization is affected by the size of the micelles and not by the total surfactant concentration as expressed by Equation (l). This micellar size effect was believed to be the reason why a nonlinear, i.e., a convex curve, relationship between In Rp and In Cg was obtained with emulsion polymerization systems of changing surfactant... 

Therefore, the "micellar size effect" offers, at least, an explanation for the variations observed in the x-values in emulsion polymerization with various monomer-surfactant combinations. Verification of this argument in detail is under investigation, however, and discussion of these results is beyond the scope of the present paper. 

Experimental results and interpretations so far presented lead to the justification of proposing a hypothesis concerning the micellar size effect on particle nucleation in mixed surfactant systems of emulsion polymerization. Essentials of this hypothesis are as follows ... 

The energetics and kinetics of film formation appear to be especially important when two or more solutes are present, since now the matter of monolayer penetration or complex formation enters the picture (see Section IV-7). Schul-man and co-workers [77, 78], in particular, noted that especially stable emulsions result when the adsorbed film of surfactant material forms strong penetration complexes with a species present in the oil phase. The stabilizing effect of such mixed films may lie in their slow desorption or elevated viscosity. The dynamic effects of surfactant transport have been investigated by Shah and coworkers [22] who show the correlation between micellar lifetime and droplet size. More stable micelles are unable to rapidly transport surfactant from the bulk to the surface, and hence they support emulsions containing larger droplets. 

We hav shown that with the use of a mixed surfactant system in styrene emulsion polymerization, the composition of the mixed surfactant has an effect on the rate of polymerization, the number of particles formed and the particle size distribution. We have also shown that a change in the ratio, r of the two surfactants in the mixture results in a considerable change in the micellar weight of the resultant mixed micelles. We have thus proposed and proven that the efficiency of nucleation of particles (even when the same number of micelles is used in the experiment) is dependent on the size of the mixed micelle, and that there is an optimum size at which the polymerization rate is the fastest and the particle size distribution is the narrowest. 

When aqueous diffusional barriers on each side of the lipoidal membrane are included, Pick s law does not fully hold in this case of protonation of weak bases. The transfer of amidopyrine and salicylic acid through an organic liquid obeys the theoretical equation proposed5. The formation of complexes can modify the rate of transfer of drugs through such barriers and demand modification of the diffusional equations . When micron-sized emulsion droplets act as sinks for drug, equations were derived for micellar solubilization to take into account the possible effects of an ... 

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