Full Molecular Weight Distribution in RAFT Polymerization. New Mechanistic Insight by Direct Integration of the Equations

The full molecular weight distribution (FMWD) equations in RAFT polymerization are solved by direct integration for three models: intermediate radical termination (IRT), slow fragmentation (SF), and IRT with oligomers (IRTO). It is shown that the quasi steady state approximation (QSSA) is always applicable to living radicals, and also applicable to intermediate radicals in the IRT and IRTO models. The application of the QSSA allows for considerable simplification of the numerical solution of the equations. A marked bimodality is found for the FMWD of the SF model only. This suggests model discrimination by radical trapping experiments followed by GPC measurement of the total MWD. magnified image