Oxygen Sensitivity of RAFT Polymerization – A Modeling Study

Reversible addition-fragmentation chain-transfer polymerization, or RAFT, is a method for the controlled synthesis of block copolymers and an alternative to living ionic polymerizations. Although it is less susceptible to impurities, oxygen leads to inhibition of the polymerization. In a previous study, a model was developed to describe the inhibition kinetics of the RAFT polymerization of styrene. Based on this model, a detailed sensitivity analysis is performed with respect to the kinetic coefficients. While the formation of polyperoxides by oxygen addition shows high reaction rates, their further reactions (growth and termination) could be identified as rate-determining steps. In addition, a proportional dependence of the duration of inhibition on the oxygen concentration was found. Based on the knowledge gained, a new initiation strategy with different thermal initiators to optimize polymerization was successfully tested using simulations.