EFFECTS OF CROSS-LINKING ON THE MORPHOLOGY OF STRUCTURED LATEX-PARTICLES .1. THEORETICAL CONSIDERATIONS

Cross-linking of the seed latex polymer introduces elastic forces into the thermodynamic analysis of the morphology of composite particles. By determining the elastic storage energy necessary to maintain a defo rmation within the seed latex particle (as in an occlusion of second-s tage polymer), it can be combined with the interfacial energies intern al to the particle and at its aqueous phase boundary to compute the to tal free energy of a specific particle morphology. At low levels of cr oss-linking it is found that the elastic and interfacial energies are of the same order of magnitude, with the final morphology determined b y the balance between them. Elastic energies are dependent upon the st ate of deformation within the particle, and this makes the thermodynam ic equilibrium morphology analysis dependent upon cross-link level, se ed latex particle size, stage ratio (second polymer/seed polymer), and the interfacial tensions at the polymer/polymer and polymer/water int erfaces. Computational results are presented which show the effects of each of these variables on the predicted morphology.