Investigation On Diffusional Behavior Of Water-Insoluble Chain Transfer Agents In Emulsion Polymerization

Chain Transfer Agents (CTAs), as a sort of effective reagent for regulating the molecular weight and molecular weight distributions (MWDs) of polymers, is widely used in the industrial production behavior. However, the effect of CTAs can be exerted only if the entry of CTAs into the major loci of emulsion polymerization, polymer particles, is successfully achieved. So it is necessary to investigate the diffusional behavior of CTAs, especially the water-insoluble CTAs in the emulsion polymerization.In the article, the emulsion containing polymer particles was first prepared by batch emulsion polymerization, then the solution of monomer and CTA was added to implement the semi-batch emulsion polymerization, and the difrusional behavior of water-insoluble dodecyl-mercaptan was discussed, in contrast with the one got from the experiment of water-soluble amyl-mercaptan.The model proposed by Momura shows that the diffusion of CTA in emulsion polymerization is realized by its passing through monomer droplet/water/polymer particles. By combining the analysis on the data of our experiment, it is obvious to find that the amyl-mercaptan diffused fast through the water phase due to its good solubility in water while the diffusion of dodecyl-mercaptan was affected by the mass transfer resistance in the water phase, due to its water insolubility. Further study also indicates that elevation of temperature and enlargement of the interface could improve the diffusional ability of CTAs in heterogeneous system.