Swelling equilibrium, latex particles with

Modeling the Equilibrium Swelling of Latex Particles with Monomers... 

It is usual to consider the course of emulsion polymerization to proceed through three intervals [16,17]. The particle number increases with time in Interval I, where latex particles are being formed, and then remains constant during Intervals II and II. The monomer concentration in particles is in equilibrium with a monomer saturated aqueous solution. Swelling is limited only by the opposite force of the particle surface/water tension. Hence, the concentration of monomer in the particles is usually taken as constant up to the point where free monomer droplets disappear. In Intervals I and II, the monomer concentration... 

This relation has been tested by Morton, who determined values of and y from equilibrium swelling measurements of polystyrene latices. The results obtained were in good agreement with values of and y (54) determined by other methods. Allen (J) measured the swelling of natural rubber latex with methyl methacrylate and found the dependence of swelling on particle size to agree well with the above equation. 

Values for the propagation rate constant can be determined from bulk or solution experiments. Values of k have been published for a wide variety of monomers as a function of temperature. With standard emulsion polymerization recipes the value of [M]p is determined from equilibrium swelling measurements if a free monomer phase is present and by a mass balance if all the monomer is in the polymer particles. One normally assumes that [M] is not dependent on particle size in latexes comprised of different-sized particles. This assumption will be questionable in some systems, especially those involving high-swelling particles. 

Chen et al. [39] and Jonsson et al. 140,41] independently proved that the composite particle morphology could be brought towards the equilibrium morphology predicted by the thermodynamic model by a post-polymerization swelling treatment of the composite latexes with solvents. 

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