Progress in predicting latex-particle morphology and projections for the future

The ability to predict the structure of composite latex particles has improved markedly since the introduction of free energy analyses of the phase separated particles. Such analyses have highlighted the importance of the interfacial tensions at the polymer/water and polymer/polymer interfaces. The variation of these interfacial tensions with important parameters such as surfactant level, polymer type, monomer concentration, and initiator end groups can be utilized to predict equilibrium particle morphology in a straightforward manner. All possible structures can be displayed on a surface energy map and the morphology with the lowest free energy can be easily located. The present challenge is to be able to determine the simultaneous effect of all of the important variables on the various interfacial tensions. The future challenge is to move away from the thermodynamic equilibrium constraints of the free energy approach and to describe the dynamic changes of the internal particle phase structure resulting from polymerization reaction within the particle.