A Modeling Study on the RAFT Polymerization of Vinyl Monomers in Supercritical Carbon Dioxide

The kinetic modeling of reversible addition-fragmentation chain transfer (RAFT) dispersion homopolymerization of vinyl monomers in supercritical carbon dioxide is addressed. The model accounts for two reaction loci, a polymer-rich phase (dispersed) and a solvent-rich phase (continuous). In one of the models, the partition of low molar mass components is estimated by using simple equations. The second model takes into account mass transfer of the components and is built using the phase-exchange and k(s)-termination steps of the Predici software. Model predictions are compared against experimental data of polymerization of styrene using 2,2-Azobis(2-methylpropionitrile) (AIBN)/S-thiobenzoyl thioglycolic acid/supercritical carbon dioxide. The model captures well the effect of the amount of RAFT agent on polymerization rate and molar mass development. Both models allow calculation of the concentrations of all the species present in the system for each phase. The performance of the system is compared against the conventional case (in the absence of RAFT agent).