Polymeric surfactants critical coagulation concentration

Further studies also deal with the use of the dodecyl moiety of the allylic compound SAAS (already studied by Urquiola [36] in the semibatch polymerization of butyl acrylate. Such surfactant was reported to behave like SDS, with the fraction of chemically incorporated surfactant hurried inside the particles increasing with the size of the particles [60]. A study of the stability of these latexes was recently reported, showing the influence of the shear rate during the polymerization, as well as the critical coagulation concentration (CCC) in the presence of electrolytes [61],... 

As an even more explicit example of this effect Figure 6 shows that EPM is able to reproduce fairly well the experimentally observed dependence of the particle number on surfactant concentration for a different monomer, namely methyl methacrylate (MMA). The polymerization was carried at 80°C at a fixed concentration of ammonium persulfate initiator (0.00635 mol dm 3). Because methyl methacrylate is much more water soluble than styrene, the drop off in particle number is not as steep around the critical micelle concentration (22.) In this instance the experimental data do show a leveling off of the particle number at high and low surfactant concentrations as expected from the theory of particle formation by coagulative nucleation of precursor particles formed by homogeneous nucleation, which has been incorporated into EPM. 

The surface tension of the continuous phase of a polymer emulsion during emulsion polymerization may be used as a measure of the free emulsifier concentration. The term free emulsifier is used here to denote surfactant which is dissolved in the aqueous phase rather than being adsorbed onto polymer particles or monomer droplets, or aggregated into micelles. The free-emulsifier concentration is widely considered to be a critical variable in particle nucleation, steady-state oscillation in a CSTR, and in preventing coagulation during polymerization. 

---