Molecular weight distributions in styrene polymerization with asymmetric bifunctional initiators

We model the molecular weight distribution (MWD) of polystyrene obtained using asymmetric bifunctional initiators. We do that by extending an existing model able to predict conversions and average molecular weights. By applying probability generating functions to the mass balances, a finite set of differential equations is obtained. This set must be solved and numerically inverted in order to obtain the MWD. Validation was performed using available experimental data on average molecular weights. Those calculated from the predicted MWD agree well with the reported experimental data. In order to show the potential of the model as a tool to tailor MWD, we use it to evaluate operating conditions in a batch reactor that would result in bimodal MWD.