Deconvolution of Molecular Weight Distributions Using Dynamic Flory-Schulz Distributions

Abstract

Summary: The deconvolution of molecular weight distributions (MWDs) may be useful for obtaining information about the polymerization kinetics and properties of catalytic systems. However, deconvolution techniques are normally based on steady-state assumptions and very little has been reported about the use of non-stationary approaches for the deconvolution of MWDs. In spite of this, polymerization reactions are often performed in batch or semi-batch modes. For this reason, dynamic solutions are proposed here for simple kinetic models and are then used for deconvolution of actual MWD data. Deconvolution results obtained with dynamic models are compared to deconvolution results obtained with the standard stationary Flory-Schulz distributions. For coordination polymerizations, results show that dynamic MWD models are able to describe experimental data with fewer catalytic sites, which indicates that the proper interpretation of the reaction dynamics may be of fundamental importance for kinetic characterization. On the other hand, reaction dynamics induced by modification of chain transfer agent concentration seem to play a minor role in the shape of the MWD in free-radical polymerizations. This Figure illustrates that MWDs obtained at unsteady conditions should not be deconvoluted with standard steady-state Flory-Schulz distributions.