Development of a kinetic model for iniferter controlled/'living' free-radical polymerization considering diffusion-controlled effects

摘要

A kinetic model incorporating the effects of diffusion-controlled reactions on INIFERTER (initiator-transfer agent0terminator) thermal free-radical polymerization has been developed. Molecular weight development is done using the method of moments. Diffusion-controlled effects are modeled using free-volume theory. The reactions considered to be diffusion-controlled are; monomer propagation, bimolecular radical termination, dormant termination, chain transfer to monomer, and chain transfer to iniferter. Radical generation by thermal self-initiation is also included in the model. Model predictions indicate that diffusion-controlled propagation reduces the "living" behavior of the system, whereas a diffusion-controlled termination enhances its livingness. The livingness of the system is also enhanced by diffusion-controlled dormant termination. When diffusion-controlled termination is important, our simulations show that the overall effect of the diffusion controlled phenomena in iniferter polymerization is to enhance the livingness of the system. Experimental data from the literature for styrene, and methyl methacrylate homopolymerizations have been used to validate the kinetic model. The agreement is reasonably good.