Miniemulsion Polymerization with Cationic and Nonionic Surfactants:  A Very Efficient Use of Surfactants for Heterophase Polymerization

The principle of miniemulsion polymerization is extended to cationic surfactants, i.e., CTAB, CTMA 2 tartrate, and CTMA 2 terephthalate, and nonionic surfactants, i.e., Lutensol AT50. Similar molecular amounts of the cationic surfactant CTAB compared to the anionic surfactant SDS result in similar particle sizes. The cationic counterion-coupled gemini surfactants (cocogems) show only moderate activity in miniemulsification. Surface tension measurements were used to determine the surface coverage and therefore the efficiency of the surfactants in the miniemulsification process. The data for the different latexes show that the underlying energetic rules of miniemulsions are different from microemulsions. It is speculated that for miniemulsions the ability for surface spreading is advantageous whereas low absolute interface energies and a high area requirement per surfactant are favorable for microemulsions. Reaction calorimeter data are also presented to show that the concept of the miniemulsion polymerization is essentially a 1:1 copying of the original droplets, possessing no complicated dependence of kinetics and particle size on the amount and locus of initiation as found for emulsion polymerization.