A comparison of reaction mechanisms for reversible addition-fragmentation chain transfer polymerization using modeling tools

A kinetic model based on a detailed reaction mechanism of the reversible addition-fragmentation transfer (RAFT) polymerization was developed. By neglecting some reactions, or using simplifying assumptions, three different reaction mechanisms proposed in the literature can be described with this model. The resulting equations were solved using a self-developed Fortran code. The cases were also modeled using the Predici trademark commercial software. Parameter sensitivity analyses and a comparison of performance of the models for the different reaction mechanisms are presented. It was found that the simplest reaction mechanisms considered in this paper cannot adequately describe the behavior of the RAFT polymerization process. It is demonstrated that the controversy in the literature regarding the six orders of magnitude difference in the fragmentation rate coefficient, and the concern about the validity of the commercial software package Predici trademark to represent the RAFT mechanism have nothing to do with model inadequacy or the alluded empirical nature of Predici trademark . Rather, these issues are merely a matter of not having precise parameter estimates in a very complex, multi-parameter model, where similar model profiles can be generated with different combinations of model parameters.