| Abstract: | For systems of emulsifier-free emulsion polymerization having particle diameter (Dp) greater than 0.15–0.2μm, a shell-growth mechanism for particle growth was proposed. According to the mechanism, the polymeric radicals can propagate only within the shell region having a thickness about equal to the most probable end-to-end distance of the terminated polymer. This mechanism was considered to result from anchoring of hydrophilic ends of the growing radicals on the particle surface and from a high average number of radicals per particle. The occurrence of limiting conversion for such large particles was attributed to the consequence of shell-region polymerization characteristic of large emulsion particles and a monomer-diffusion-controlled polymerization mechanism within the particles during the high conversion period. |
